BUTTE , Montana ( CNN ) -- Three families with young children were heading to a ski vacation together when their plane crashed into a cemetery in Montana , loved ones of the victims said Monday . Dr. Erin Jacobson and his family , shown here in a photo from November , were killed in the crash . Federal investigators said that with no flight data recorder or cockpit voice recorder on the plane and no survivors , an investigation into what caused the crash could last months . `` This is going to take a while , '' National Transportation Safety Board Acting Chairman Mark Rosenker said at a news conference Monday . Investigators are looking into whether the single-engine plane was overloaded , what role weather may have played in the accident and what made the pilot decide to divert to Butte , he said . He urged reporters not to `` jump to conclusions '' about the crash . Early speculation focused on the fact that there were 14 people aboard the 10-seat aircraft , but Rosenker said young children often travel on the laps of adult passengers and urged reporters not to rush to judgment about the cause of the crash . `` To jump to conclusions is a disservice to your readers and to those who are watching your broadcasts , '' he said . `` This will be a long and tedious investigation -- extremely thorough . We will look at every factor which could affect the performance of this aircraft . '' Investigators said seven adults and seven children were on board , and all died in the crash Sunday . Authorities have not publicly identified the victims . But colleagues and loved ones have named all 14 . Watch friend describe how victim was `` like family '' » . On Monday some of the victims ' relatives visited the site of the wreck . St. Helena Hospital in St. Helena , California , said an ophthalmologist who worked there was killed , along with his family . `` The St. Helena Hospital family is filled with such deep sadness over the deaths of Dr. Erin Jacobson , his wife Amy , and their three children , Taylor , Ava and Jude , '' the hospital said in a written statement , adding , `` Our thoughts and prayers are with the families and friends of each victim of this terrible tragedy . '' A friend of the Jacobson family said the Jacobson children were 4 , 3 , and 2 years of age . A dental practice in Valley Springs , California , said dentist Michael Pullen and his wife , Vanessa , were on the plane with their 9-year-old daughter , Sydney , and 7-year-old son , Christopher . The family is from Galt , California . Dr. James DuHamel of DuHamel & Pullen Family Dental said the two families were related . Vanessa Pullen , a physician in Elk Grove , was the sister of Amy Jacobson , he said . DuHamel said Pullen was `` a fantastic dentist , '' and added that he will `` miss him greatly . '' Adrian Cotton , whose wife is a sister of Vanessa Pullen and Amy Jacobson , is acting as a spokesman for the families . The third family was that of Dr. Brent Ching , a dentist in Chico , California , his office confirmed without providing further comment . Ching was accompanied by his wife Kristen and children Hailey , 5 , and Caleb , 3 , Hostetter said . Cotton said the pilot on the plane was Bud Summerfield , who was not related to any of the victims . While investigators continue to look into the crash , it is unclear whether details of what happened will ever be known . There is no requirement for a cockpit voice recorder or a flight data recorder on such private planes . Rosenker said there might be some avionics -- electronic systems that private planes can use for a variety of purposes -- that might contain some information , though they are not built to withstand crashes . A CNN crew at the crash site , Holy Cross Cemetery , could see no large chunks of the plane , a single-engine Pilatus PC-12 . But Rosenker said `` portions of all major structural components '' had been identified . Watch footage from the crash site » . Some visitors set up crosses outside the gates of the cemetery to serve as a makeshift memorial . Others brought flowers . The flight was headed to Bozeman , Montana , but was rerouted to Butte , said Federal Aviation Administration spokesman Mike Fergus . The plane crashed 500 feet short of the runway at Bert Mooney Airport . No one was injured on the ground , Sheriff John Walsh said . The weather , which was clear Sunday , does not appear to have been a factor . See a map of the crash site » . The plane was designed to carry 11 people -- two in the cockpit and nine in the cabin , said Rosenker . He noted that young children often travel on the laps of adult passengers . Martha Guidoni said she and her husband witnessed the plane crash . She photographed one of the first images from the scene , which showed the cemetery in the foreground of a huge blaze . iReport.com : iReporter at scene of crash . `` We were just taking a ride -- all of a sudden , we watched this plane just take a nosedive , '' she said . `` We drove into the cemetery to see if there was any way my husband could help someone . We were too late -- there was nothing to help . '' Her husband , Steve Guidoni , said the plane `` went into the ground '' and ignited a tree . `` I looked to see if there was anybody I could pull out , but there was n't anything there ; I could n't see anything , '' he said . `` There was some luggage strewn around . ... There was some plane parts . '' Watch witness describe what he saw » . A flight plan said the plane originated in Redlands , California , according to flight-tracking site FBOweb.com . Stops were made in Vacaville and Oroville , California , before the plane headed for Montana . The plane stopped at the Oroville airport about 11 a.m. , refueled and departed about half an hour later , said Police Chief Kirk Trostle . The Oroville airport does not have a control tower . Eric Teitelman , Oroville 's director of community development and public works , said that because it has a `` wide-open runway '' and a self-service fuel system , it is a frequent stop for general aviation aircraft . There were conflicting reports about ownership of the plane , which was manufactured in 2001 . CNN 's Auggie Martin , Dan Simon , Jim Spellman , Mike Ahlers and Irving Last contributed to this report .
Some family members of 14 victims visit scene of crash . Investigators looking into whether the single-engine plane was overloaded . FAA says 7 children , 7 adults were aboard plane that crashed in Butte , Montana . No recorders aboard ; it 's not clear whether details of the crash will ever be known .