(CNN) German investigators found antidepressants in the apartment of Germanwings co-pilot Andreas Lubitz this week, according to published reports. 
 
 Die Welt, a German newspaper, cited an unidentified senior investigator who said Lubitz suffered from a severe "psychosomatic illness" and German police seized prescription drugs that treat the condition. Lubitz suffered from a "severe subjective burnout syndrome" and from severe depression, the source told Die Welt. 
 
 The New York Times also reported that antidepressants were found during the search of his apartment. CNN has not been able to confirm the reports. 
 
 Investigators continued to work Saturday to piece together the secret life of Lubitz, who officials say was hiding an illness from his employers. He had been declared "unfit to work" by a doctor. 
 
 They were expected to question his relatives, friends and co-workers as they try to pin down what could have prompted the seemingly competent and stable co-pilot to steer a jetliner into a mountainside on Tuesday. 
 
 As their efforts continued, dozens of people attended a remembrance ceremony for the victims of the crash at a church in a nearby town, Digne-les-Bains. There were 150 people on board Germanwings Flight 9525, including Lubitz. 
 
 Relatives of the victims and local residents also gathered Saturday afternoon by a simple stone memorial set up near the crash site, in the village of Le Vernet. Flowers have been laid there, in the shadow of the snow-covered peaks of the French Alps. 
 
 JUST WATCHED Police search Germanwings co-pilot's home for clues Replay More Videos ... MUST WATCH Police search Germanwings co-pilot's home for clues 00:10 
 
 Mental health speculation 
 
 Much attention has focused on Lubitz's state of mind, with some media reports speculating that he may have had mental health issues. 
 
 Investigators found a letter in the waste bin of his Dusseldorf, Germany, apartment saying that Lubitz, 27, wasn't fit to do his job, city prosecutor Christoph Kumpa said Friday. The note, Kumpa said, had been "slashed." 
 
 Just what was ailing Lubitz hasn't been revealed. The New York Times and the Wall Street Journal, citing unnamed sources, reported Friday that Lubitz suffered from mental illness and kept his diagnosis concealed from his employer. 
 
 A subsequent New York Times report on Saturday, citing two officials with knowledge of the investigation, said Lubitz sought treatment before the crash for vision problems that might have put his career at risk. According to those unnamed officials, Lubitz also was being treated for psychological issues. Other media reports indicate he was treated for depression. 
 
 Lubitz passed his annual pilot recertification medical examination in summer 2014, a German aviation source told CNN. 
 
 An official with Lufthansa, which owns Germanwings, said the exam only tests physical health, not psychological health, and that if Lubitz had vision problems that would have been discovered during the tests. 
 
 "We can't believe it. If anything was wrong with his eyes during the physical exam we would have known," the official says. 
 
 The Lufthansa official also said the company was never given any indication Lubitz was depressed, and that if he went to a doctor on his own he would have been required to self-report if he had been deemed unfit to fly. 
 
 A Dusseldorf clinic said he'd gone there twice, most recently on March 10, "concerning a diagnosis." But the University Clinic said it had not treated Lubitz for depression. 
 
 German investigators said they still have interviews and other work to do before they can reveal what they gleaned from the records found in the apartment and at his parents' home in the town of Montabaur. 
 
 JUST WATCHED Prosecutor: Co-pilot hid 'illness' from airline Replay More Videos ... MUST WATCH Prosecutor: Co-pilot hid 'illness' from airline 02:40 
 
 But the fact that investigators found "ripped, recent medical leave notes, including for the day of the offense, leads to the preliminary conclusion that the deceased kept his illness secret from his employer and his professional environment," prosecutors said. 
 
 Germanwings corroborated that assertion, saying it had never received a sick note from Lubitz. 
 
 Authorities left Lubitz's apartment Friday night with boxes of papers and evidence folders after spending about 90 minutes inside. 
 
 Investigators exchange information 
 
 Dusseldorf police said Saturday that a small team of French investigators had arrived in the city and that they were sharing information. 
 
 Jean Pierre Michel, lead investigator for the French inquiry, told French TV from Dusseldorf that the French team would work in "full transparency" with their German counterparts. 
 
 "We will interview people related to the investigation in the coming days. The hearings will be conducted in the coming days and weeks," he said, according to CNN's French affiliate BFMTV. 
 
 Asked by a journalist about reports of Lubitz's possible mental illness, he replied: "The elements of the investigation are strictly confidential and we cannot address these matters today." 
 
 No scenario can yet be ruled out, including mechanical failure, "as we do not have the necessary evidence," he said. 
 
 The German tabloid newspaper Bild said Saturday it had interviewed an ex-girlfriend of Lubitz. The woman is not named in the story and CNN has not been able to verify the report independently. 
 
 According to Bild, the ex-girlfriend said Lubitz was a very nice and sensitive man who needed a lot of care and attention, and he was very troubled. She said he would get into fights with her. 
 
 The newspaper also cited the ex-girlfriend as saying that Lubitz had bad dreams that his plane was going down. 
 
 Relative names flight captain 
 
 Patrick Sondenheimer was the pilot of Germanwings Flight 9525, according to Reiner Sondenheimer of Dusseldorf, Germany, who says he is a relative of Patrick's. 
 
 Patrick Sondenheimer is the pilot believed to have been locked out of the cockpit by his co-pilot, Lubitz. 
 
 JUST WATCHED Germanwings pilot identified Replay More Videos ... MUST WATCH Germanwings pilot identified 01:38 
 
 CNN spoke to Reiner Sondenheimer at his Dusseldorf apartment. Also at the apartment was a woman who did not provide her name but said she was Patrick Sodenheimer's relative. That woman also said that Patrick Sondenheimer was on the doomed flight. 
 
 Reiner Sondenheimer declined to say anything else, other than the family wanted time to grieve. 
 
 The pilot has not been named by German authorities. 
 
 Another Germanwings pilot who once flew with Lubitz, Frank Woiton, told WDR, a local broadcaster belonging to CNN's German affiliate ARD, that his impression of Lubitz was that he was "friendly" and that there was "nothing suspicious." 
 
 Woiton also said Lubitz "was a good pilot and had a good command of the plane." 
 
 Woiton's first job after he found out about the crash was the route Dusseldorf-Barcelona-Dusseldorf -- the same route as had been taken by Germanwings Flight 9525 a day earlier. 
 
 He was praised in German media for the emotional announcement he made to passengers before takeoff, in which he said the crew, like everyone else on the plane, wanted to get home safely to their families. 
 
 Perilous recovery operation 
 
 At the scene of the crash, two helicopters were being deployed above the mountainside by recovery crews Saturday. The weather has improved after high winds Friday made their complex task even more treacherous 
 
 Lt. Col. Xavier Vialenc, a spokesman for the Gendarmerie, told CNN there were about 40 officers at the crash site Saturday. 
 
 Once at the crash site, recovery workers spend all day working there, he said. Back in Seyne-les-Alpes at the end of the day, they can see a psychologist if they choose and have a debriefing session with all the workers. 
 
 Vialenc said the operations were going well so far and that the progress made was meeting their expectations. 
 
 Yves Naffrechoux, captain of rescue operations at Seyne-les-Alpes, told CNN on Friday that rescuers have found bodies at the rugged crash site, but few of them are intact. 
 
 JUST WATCHED Investigators: Recovery effort going 'bit by bit' Replay More Videos ... MUST WATCH Investigators: Recovery effort going 'bit by bit' 02:10 
 
 It could be weeks before all the bodies are recovered, identified and released to the families, authorities said. 
 
 The mountainous terrain where the Germanwings jet went down is difficult to access. 
 
 Airline: Lubitz passed initial tests 
 
 What could have prompted Lubitz to deliberately destroy the aircraft, killing everyone on board, remains the focus of investigators in Germany. 
 
 JUST WATCHED Lufthansa CEO: Speechless that co-pilot crashed plane Replay More Videos ... MUST WATCH Lufthansa CEO: Speechless that co-pilot crashed plane 01:08 
 
 He had passed medical and psychological testing when he was hired in 2013, said Carsten Spohr , CEO of Lufthansa, which owns Germanwings. 
 
 Spohr also told reporters that Lubitz had "interrupted" his pilot training, which he began in 2008. That break lasted several months, he said, but added that such an interruption isn't uncommon. Spohr didn't give a reason for the break. 
 
 While the ailment Lubitz had sought treatment for hasn't been revealed, that he was declared unfit for work is an important detail, aviation analysts say. Pilots are required to maintain their fitness to fly and must tell their airline if they're found unfit, CNN aviation analyst David Soucie said. 
 
 Although authorities have recovered the cockpit voice recorder, the flight data recorder remains missing. It could shed crucial details about what happened inside the cockpit, authorities say. 
 
 Banging and screaming 
 
 Lubitz was the co-pilot on Tuesday's flight between Barcelona, Spain, and Dusseldorf when he apparently locked the captain out of the cockpit, then activated a control causing the plane to descend toward rugged terrain. 
 
 Germanwings said the plane dropped for about eight minutes from its cruising altitude of 38,000 feet before crashing. 
 
 The only sounds , authorities said, were those of pounding on the cockpit door, Lubitz's steady breathing and, eventually, screaming passengers. 
 
 Lubitz and 149 other people on board the plane died in an instant, authorities say. Most were from Germany and Spain. ||||| Media playback is unsupported on your device Media caption Co-pilot Andreas Lubitz, seen here on his Facebook profile, controlled the plane's descent, Marseille prosecutor Brice Robin said 
 
 The man suspected of deliberately crashing a Germanwings A320 plane in the French Alps required treatment for depression, German media say. 
 
 Regular assessments were recommended in Andreas Lubitz's official notes after a serious episode some years ago. 
 
 The Barcelona-Duesseldorf plane crashed on Tuesday, killing 150 people. 
 
 Data from the plane's voice recorder suggest Mr Lubitz purposely started a descent as the pilot was locked out of the cockpit. 
 
 Several airlines have now pledged to change their rules to ensure at least two crew members are present in the cockpit at all times. 
 
 Police have searched two German properties used by Mr Lubitz, taking away boxes and a computer. 
 
 'Heavily depressive' 
 
 When Mr Lubitz finished training in 2009, he was diagnosed with a serious depressive episode and went on to receive treatment for a year and a half, the German news site Bild reports. 
 
 Internal documents quoted by Bild and German broadcaster ARD say a note on Mr Lubitz's aviation authority file recommended regular psychological assessment. 
 
 Andreas Lubitz: Germanwings co-pilot under scrutiny 
 
 Started training in 2008, at Bremen and Arizona. Training was interrupted for some months - but he later passed all tests and was deemed fit to fly 
 
 Working as co-pilot, or first officer, since 2013. Appeared pleased with his job 
 
 Lived in town of Montabaur, near Frankfurt, reportedly with his parents. Kept a flat in Duesseldorf and had many friends 
 
 Facebook profile suggests the active lifestyle of a keen runner, with an interest in pop music 
 
 Who was Andreas Lubitz? 
 
 Mr Lubitz's employers have confirmed that his training was interrupted for several months six years ago. 
 
 But they have not said why. Carsten Spohr - the head of Lufthansa, the German carrier that owns Germanwings - said on Thursday that Mr Lubitz was only able to resume training after his suitability was "re-established". 
 
 "He passed all the subsequent tests and checks with flying colours," Mr Spohr was quoted as saying. 
 
 German media are also reporting that investigators have found evidence of mental health problems at Mr Lubitz's Duesseldorf flat. 
 
 Earlier, another media report quoted a police spokesman as saying "a very significant clue as to what has happened" had been found during the search of the house the 27-year-old shared with his parents in Montabaur, north of Frankfurt, without specifying what. 
 
 Police said the discovery was not a suicide note. 
 
 French Prime Minister Manual Valls said the investigation was ongoing, but that "everything is pointing to a criminal, crazy, suicidal action that we cannot comprehend". 
 
 He said investigators and Lufthansa would have to "shed light on the career and profile of this pilot". 
 
 Image copyright Reuters Image caption Mr Lubitz is said to have been an enthusiastic runner and is here pictured running a half-marathon in September 2009 
 
 Image copyright AP Image caption Police have been coming and going at the home of Mr Lubitz's parents north of Frankfurt, which is also the focus of a media spotlight 
 
 Image copyright AFP Image caption Families of the crash victims visited Seyne-les-Alpes, a town close to the crash site 
 
 Image copyright Getty Images Image caption In the hamlet of Vernet, a "viewing tent" was set up where families could look in the direction of the crash site. Families laid flowers and photographs in memory of those lost. 
 
 Police continued to come and go at the Montabaur house throughout Thursday morning, reports the BBC's Anna Holligan who is outside. 
 
 She says there are concerns for Mr Lubitz's parents, who have suffered not just one trauma - their son dying in a crash - but the subsequent shock of finding out he may have been responsible for the tragedy. 
 
 Axe 
 
 Based on data from the recovered "black box" voice recorder, Marseille prosecutor Brice Robin said on Thursday that Mr Lubitz appeared to want to "destroy the plane". 
 
 The evidence suggested the pilot had left the cockpit, probably to go to the toilet, during which the door was barred. He fought unsuccessfully to get back in, he said. 
 
 Bild quotes security sources as saying that the pilot used an axe to try to break down the door. 
 
 A Germanwings spokesperson would only confirm that an emergency axe is part of the equipment on board an A320. 
 
 Media playback is unsupported on your device Media caption Rescuer Jean Sebastien Beaud describes the plane crash scene as "surreal" 
 
 What happened in the final half hour? 
 
 Family members of some of the 150 passengers and crew who died have visited Seyne-les-Alpes, near the crash site, reported Reuters news agency. 
 
 They were accompanied by psychologists, paramedics and Red Cross workers, and a youth centre in the town was set up to receive them, it said. 
 
 Families are providing DNA samples to allow for identification of victims' remains. 
 
 Meanwhile, investigators continue to comb the crash site for body parts, debris and the second "black box", which records flight data and still has not been found three days after the plane crashed. 
 
 Flight club 
 
 Members of the Westerwald flight club, where the co-pilot was a member, expressed their shock at the revelations about Mr Lubitz's mental history. 
 
 Media playback is unsupported on your device Media caption Members of the flight club where Andreas Lubitz was a member have been talking about his personality 
 
 "Andreas was a very nice young man, who did his training here. He was part of the club," Peter Reucker said. 
 
 "[He was] funny, sometimes a bit quiet, but apart from that a young man like many others that we have here. He integrated well. 
 
 "I'm absolutely speechless. I have no explanation for this," Mr Reucker added. 
 
 Crash site close-ups 
 
 Other incidents thought to be caused by deliberate pilot action 
 
 29 November 2013: A flight between Mozambique and Angola crashed in Namibia, killing 33 people. Initial investigation results suggested the accident was deliberately carried out by the captain shortly after the first officer (also known as the co-pilot) had left the flight deck. 
 
 A flight between Mozambique and Angola crashed in Namibia, killing 33 people. Initial investigation results suggested the accident was deliberately carried out by the captain shortly after the first officer (also known as the co-pilot) had left the flight deck. 31 October 1999: An EgyptAir Boeing 767 went into a rapid descent 30 minutes after taking off from New York, killing 217 people. An investigation suggested that the crash was caused deliberately by the relief first officer but the evidence was not conclusive. 
 
 An EgyptAir Boeing 767 went into a rapid descent 30 minutes after taking off from New York, killing 217 people. An investigation suggested that the crash was caused deliberately by the relief first officer but the evidence was not conclusive. 19 December 1997: More than 100 people were killed when a Boeing 737 travelling from Indonesia to Singapore crashed. The pilot - suffering from "multiple work-related difficulties" - was suspected of switching off the flight recorders and intentionally putting the plane into a dive. 
 
 Source: Aviation Safety Network ||||| Image copyright AFP Image caption The German tabloid Bild carried an interview with the ex-girlfriend of Germanwings co-pilot Andreas Lubitz (pictured) 
 
 The Germanwings co-pilot thought to have deliberately crashed his Airbus in the French Alps, killing 150 people, predicted "one day everyone will know my name", his ex-girlfriend says. 
 
 In an interview with Germany's Bild newspaper, she recalled a comment Andreas Lubitz made last year. 
 
 "One day I'm going to do something that will change the whole system, and everyone will know my name and remember," he told her. 
 
 Flight 4U 9525 crashed on Tuesday. 
 
 The woman, a 26-year-old flight attendant who flew with Lubitz for five months last year, was "very shocked" when she heard the news, the paper says. 
 
 She is referred to only as Maria W. 
 
 Image copyright AP Image caption Memorial services for those onboard flight 4U 9525 have been taking place in Germany and in Spain 
 
 If Lubitz deliberately brought down the plane, "it is because he understood that because of his health problems, his big dream of a job at Lufthansa, as captain and as a long-haul pilot was practically impossible," she told Bild. 
 
 Meanwhile, German newspaper Die Welt said that investigators had found evidence of a serious "psychosomatic illness", and that Lubitz had been "treated by several neurologists and psychiatrists". 
 
 Several medicines used to treat mental illnesses were found at his home, but there were no signs of drug or alcohol addiction, the newspaper, citing an unnamed investigator, said. 
 
 Separately, the New York Times, citing officials, reported that Lubitz had sought treatment for eye problems. 
 
 Briton's father in plea to airlines 
 
 'Too much pressure' 
 
 French investigator Jean-Pierre Michel also told the AFP news agency that the pilot's personality was "a serious lead [in the investigation] but... can't be the only one". 
 
 "We're going to try to understand what in his life could have left him to carry out the act," Mr Michel said, adding that investigators had not discovered any "particular element" so far. 
 
 The black box voice recorder indicates that Lubitz locked his captain out of the cockpit on Tuesday and crashed the plane into a mountainside in what appears to have been a suicide and mass killing. 
 
 Image copyright AFP Image caption Lufthansa and Germanwings took out full-page condolence notices in German newspapers 
 
 German prosecutors say they found medical documents at Lubitz's house suggesting an existing illness and evidence of medical treatment. They found torn-up sick notes, one of them for the day of the crash. 
 
 They say he seems to have concealed his illness from his employers. 
 
 His former girlfriend told Bild they separated, "because it became increasingly clear that he had a problem". 
 
 Media playback is unsupported on your device Media caption Ex-girlfriend: "He sometimes tended to be aggressive" 
 
 She said he was plagued by nightmares and would at times wake up screaming "we're going down". 
 
 She added that he became stressed when they spoke about work: "He became upset about the conditions we worked under: too little money, fear of losing the contract, too much pressure." 
 
 A hospital in the German city of Duesseldorf has confirmed Lubitz was a patient there recently but it denied media reports that he had been treated for depression. 
 
 Lubitz's employers insisted that he had only been allowed to resume training after his suitability was "re-established". 
 
 Image copyright Getty Images Image caption Andreas Lubitz running a half-marathon in Frankfurt in March 2010 
 
 Lubitz's health timeline 
 
 2009 : Breaks off pilot training while still in his early twenties after suffering "depressions and anxiety attacks", the German tabloid Bild reports, quoting Lufthansa medical files. Resumes training after 18 months of treatment, according to Bild 
 
 : Breaks off pilot training while still in his early twenties after suffering "depressions and anxiety attacks", the German tabloid Bild reports, quoting Lufthansa medical files. Resumes training after 18 months of treatment, according to Bild 2013 : Qualifies "with flying colours" as pilot, according to Lufthansa 
 
 : Qualifies "with flying colours" as pilot, according to Lufthansa 2013-2015 : Medical file quoted by Bild marks him as requiring "specific regular medical examination" but no details are given 
 
 : Medical file quoted by Bild marks him as requiring "specific regular medical examination" but no details are given February 2015 : Undergoes diagnosis at Duesseldorf University Clinic for an unspecified illness; clinic has clarified the illness was not depression 
 
 : Undergoes diagnosis at Duesseldorf University Clinic for an unspecified illness; clinic has clarified the illness was not depression 10 March 2015 : Again attends Duesseldorf University Clinic 
 
 : Again attends Duesseldorf University Clinic 24 March 2015 :Is believed to have deliberately crashed airliner, killing himself and 149 others 
 
 :Is believed to have deliberately crashed airliner, killing himself and 149 others 26 March 2015: Prosecutors announce that two sick notes have been found torn up at his addresses in Germany 
 
 Unanswered questions 
 
 What drives people to murder-suicide? 
 
 Who was Andreas Lubitz? 
 
 'Unfathomable loss' 
 
 A fellow member of the flight school where Andreas Lubitz took lessons told the BBC the co-pilot had known the area of the French Alps where the plane crashed from going there on gliding holidays. 
 
 A French newspaper, Metro News, reported (in French) that Lubitz had holidayed with his parents at a flying club nearby. 
 
 French police say the search for passenger remains and debris on the mountain slopes could take another two weeks. 
 
 Media playback is unsupported on your device Media caption Relatives have been visiting the site of the Alps plane crash 
 
 Relatives of some of the passengers and crew who died, including the family of the captain, have visited Seyne-les-Alpes, near the crash site. 
 
 In the aftermath of the crash, the EU's aviation regulator, the European Aviation Safety Agency, has urged airlines to adopt new safety rules. 
 
 In future, it says, two crew members should be present in the cockpit at all times. 
 
 Lufthansa and Germanwings have taken out full-page notices in German newspapers, expressing their "deepest sympathy" and condolences for "the unfathomable loss of 150 lives". 
 
 What is depression? 
 
 Depression is more than just feeling a bit down for a few days. It is an illness which, at its most severe, can leave people feeling that life is no longer worth living. It can cause physical symptoms such as headaches, sleeplessness and constant tiredness which may last for months and months. 
 
 People with depression can also feel anxious, irritable and agitated on a daily basis but it affects everyone differently and only in rare cases is it a reason for violence against others. 
 
 If people admit their symptoms and talk to someone about their feelings, depression can usually be treated but the biggest barrier to getting help is often stigma and the fear of disclosing mental health problems. 
 
 German media examine 'depression' reports 
 
 Headlines add to stigma for sufferers 
 
 More on depression 
 
 Other incidents thought to be caused by deliberate pilot action 
 
 29 November 2013: A flight between Mozambique and Angola crashed in Namibia, killing 33 people. Initial investigation results suggested the accident was deliberately carried out by the captain shortly after the first officer (also known as the co-pilot) had left the flight deck. 
 
 A flight between Mozambique and Angola crashed in Namibia, killing 33 people. Initial investigation results suggested the accident was deliberately carried out by the captain shortly after the first officer (also known as the co-pilot) had left the flight deck. 31 October 1999: An EgyptAir Boeing 767 went into a rapid descent 30 minutes after taking off from New York, killing 217 people. An investigation suggested that the crash was caused deliberately by the relief first officer but the evidence was not conclusive. 
 
 An EgyptAir Boeing 767 went into a rapid descent 30 minutes after taking off from New York, killing 217 people. An investigation suggested that the crash was caused deliberately by the relief first officer but the evidence was not conclusive. 19 December 1997: More than 100 people were killed when a Boeing 737 travelling from Indonesia to Singapore crashed. The pilot - suffering from "multiple work-related difficulties" - was suspected of switching off the flight recorders and intentionally putting the plane into a dive. 
 
 Source: Aviation Safety Network
– Police last night searched Germanwings co-pilot's Andreas Lubitz's apartment in Duesseldorf, Germany, and the home he shared with his parents in the small town of Montabaur, removing boxes of possessions and what one investigator called a potentially "significant clue" that will be taken for testing, reports the BBC. German prosecutors later announced that they found medical documents in the 27-year-old's home that indicate "an existing illness and appropriate medical treatment," reports the AP. Prosecutor Ralf Herrenbrueck further said that torn-up sick notes for the day of the crash "support the current preliminary assessment that the deceased hid his illness from his employer and colleagues." It's not clear if the notes and the "clue" are the same. Herrenbrueck says no suicide note or evidence of any political or religious motivation for Lubitz's actions were uncovered. An unconfirmed report in Germany's Bild newspaper stated that Lubitz was diagnosed with a "severe depressive episode" in 2009 and had to repeat flying classes because of depression. The German paper says Lubitz was having relationship problems with his girlfriend, and police are looking into whether he was having a "personal life crisis," the Guardian reports. So far, airline chiefs have said only that there "was a lengthy interruption in his training" six years ago and he passed all subsequent checks with "flying colors," reports Reuters.