INDIANAPOLIS -- The Marion County coroner's office said Wednesday that the pilot of a plane that crashed into an Indianapolis retention pond Monday died of blunt force trauma, and that examiners could find no evidence that he suffered a medical emergency before the crash.

Dr. Robert Edesess, who was piloting the small plane, died shortly after the crash into a pond in a west-side Indianapolis subdivision. Three passengers -- his wife, his son and a family friend -- were rescued from the craft and were listed in serious condition at Methodist Hospital.

Friends of Edesess had told the news media that doctors indicated that Edesess suffered an aneurysm or another medical emergency, and they speculated that this might have caused him to lose control of the plane. However, Deputy Coroner Alfarena Ballew said Wednesday that she saw no evidence of an aneurysm.

"There were some injuries to the head, of course. However, we didn't find anything significant in the head that would suggest that there was a natural event of an aneurysm," Ballew said.

Pathologists said Edesess had a history of cardiovascular problems, and because of that, it would be difficult to tell if he had suffered a heart problem immediately before the crash.

Jim Silliman, air safety investigator for the National Transportation Safety Board, said it could take a year to determine why the plane crashed.

Silliman said the NTSB is in the initial stages of finding facts about the pilot's medical condition, the weather and the aircraft. He said a brief, preliminary report could come in the next five or six days.

The full investigation and a report on the probable cause of the crash could take a year or longer, he said.