Image copyright AFP/ Getty Image caption The nurse, known as Niels H, was jailed for life two years ago 
 
 A nurse serving a life sentence for murdering two patients in northern Germany is now a suspect in at least 84 other murder cases, police say. 
 
 The 40-year-old, named only as Niels H under German reporting rules, was convicted of attempted murder in 2006 and murder in 2015. 
 
 His victims received lethal drug doses at units where he worked. 
 
 Relatives of patients who died in clinics where he worked had urged police to investigate further. 
 
 A commission was set up in 2014 to investigate the scale of his crimes, which could make him Germany's worst post-war killer. 
 
 The medication caused heart failure or the collapse of patients' circulatory systems. 
 
 Judges said he was motivated by a desire to win approval by resuscitating the patients he had drugged. 
 
 During his 2015 trial, he admitted applying the drug to about 90 people at an intensive care clinic in the town of Delmenhorst. 
 
 Media playback is unsupported on your device Media caption Niels H hid behind a folder during his trial 
 
 Police say the abnormalities stretch back to 2000 at another clinic in Oldenburg. 
 
 They said staff had a meeting there in 2001 to discuss the strange levels of deaths and resuscitations, but did not report the levels to police, and Niels H was able to move to the Delmenhorst clinic. 
 
 A special police commission was set up in 2014 to investigate the case. 
 
 It has been analysing hundreds of medical records and exhumed 134 bodies to test samples for drug residue. 
 
 The investigations have been made more difficult because many patients had been cremated. 
 
 "The findings continue to breach any imagination," said Oldenburg police chief Johann Kuhme. "It is simply not possible to say how many people were killed." 
 
 Mr Kuhme warned the number could still rise further. The new charges are now likely to be filed at the beginning of 2018, he said. ||||| Oldenburg police choef Johann Kuehme speaks about the current investigations into the former nurse Niels Hoegel in Oldenburg, Germany, Monday, Aug. 28, 2017. The nurse who was convicted of killing... (Associated Press) 
 
 Oldenburg police choef Johann Kuehme speaks about the current investigations into the former nurse Niels Hoegel in Oldenburg, Germany, Monday, Aug. 28, 2017. The nurse who was convicted of killing patients in Germany with overdoses of heart medication is now believed to have killed at least 84 people... (Associated Press) 
 
 BERLIN (AP) — A male nurse who was convicted of killing patients in Germany with overdoses of heart medication is now believed to have killed at least 86 people — and the true scale of the killings could be even larger, investigators said Monday. 
 
 Many of the deaths could have been prevented if health authorities had acted more quickly on their suspicions, said Johann Kuehme, police chief in the northwestern city of Oldenburg. 
 
 Niels Hoegel, now 40, was convicted in 2015 of two murders and two attempted murders at a hospital in the northwestern town of Delmenhorst. He was sentenced to life in prison. But prosecutors have long said they believe he killed many more people, last year putting the figure at 43 at least. 
 
 The crimes came to light after Hoegel was convicted of attempted murder in another case. Authorities subsequently investigated hundreds of deaths, exhuming bodies of former patients in Delmenhorst and nearby Oldenburg. 
 
 Kuehme said Monday that authorities have now unearthed evidence of 84 killings in addition to the ones for which Hoegel was convicted. The number of actual killings is likely higher because some possible victims were cremated, making it impossible to gather evidence, Kuehme added. 
 
 "Eighty-four killings ... leave us speechless," Kuehme told reporters. "And as if all that were not enough, we must realize that the real dimension of the killings by Niels H. is likely many times worse." 
 
 The fact that the cases go back many years and people may struggle to remember the exact details of their loved ones' deaths hurts authorities' ability to determine an exact number, Kuehme said. 
 
 He faulted local health authorities for being slow to act. 
 
 "If the people responsible at the time, particularly at the Oldenburg clinic but also later in Delmenhorst, hadn't hesitated to alert authorities — for example police, prosecutors —" Hoegel could have been stopped earlier, Kuehme said. 
 
 Authorities are already pursuing criminal cases against former staff at the two facilities. 
 
 Hoegel worked at the Oldenburg hospital from 1999 to 2002 and in Delmenhorst from 2003 to 2005. 
 
 Kuehme said other medical workers at Oldenburg were aware of an elevated number of resuscitations, and initial indications of possible wrongdoing by the nurse in Delmenhorst emerged as early as April 2003. 
 
 During his trial, Hoegel had said he intentionally brought about cardiac crises in some 90 patients in Delmenhorst because he enjoyed the feeling of being able to resuscitate them. 
 
 He later told investigators that he also killed patients in Oldenburg. 
 
 Prosecutors are expected to try Hoegel on at least some of the additional killings but Germany's judicial system does not allow for consecutive sentences, so future convictions won't affect his life term. 
 
 The identities of the suspected 84 victims haven't been released. There was no immediate comment Monday from any representatives of victims' families.
– He has been convicted of killing two and attempting to murder two more—and he could actually be "Germany's worst post-war killer," reports the BBC. Niels Hoegel, 40, was sentenced to life in prison in 2015 for those crimes, but prosecutors voiced their belief that the nurse had killed many more while working at clinics in Oldenburg (from 1999 to 2002) and Delmenhorst (from 2003 to 2005), reports the AP. Now police are giving a sense of just how many more: at least 84. Hoegel said at trial that he wanted to play the hero and drugged his patients so that he could then resuscitate them and win praise. Except a commission established three years ago to determine the breadth of his crimes has found that many patients ended up receiving lethal doses of drugs that brought on heart failure or destroyed the circulatory system. The BBC reports that 134 bodies have been exhumed and tested for traces of the drug, but "it is simply not possible to say how many people were killed," per Oldenburg police chief Johann Kuhme. That's in part because many of his patients were cremated. The AFP quotes chief police investigator Arne Schmidt as describing the death toll as "unique in the history of the German republic." There is "evidence for at least 90 murders," he said at a press conference, "and at least as many [suspected] cases again that can no longer be proven." Kuhme faulted the clinics for having "hesitated to alert authorities," saying the death toll could have been much lower if they had. New charges against Hoegel will likely be filed next year. (This nurse says she would get a "red surge" before killing one of her patients.)