DENVER -- NTSB investigators returned to the scene of a fatal plane crash Saturday to look for clues as to why the plane went down on Thursday afternoon in rugged terrain near Black Hawk.

"They dropped off the radar about 3:45p.m.," said Jason Aquilera from NTSB.

The 47-year-old pilot, Barry Maggert, of Carbondale, told air traffic control he was having engine problems and was going down. He was en route from Glenwood Springs to Boulder for his son’s graduation from CU.

The greatest challenge for investigators is the location of the wreckage. Crews cleared a path through the snow Friday but the debris lies on a very steep slope.

"With the angle of the plane and the engines it may not be possible to get to all the components in the field," said Aquilera.

Investigators revealed Saturday that passenger, 23-year-old Jonathan Holton, first attempted to give medical help to Maggert after the crash. Then he called for help on his cell phone. Holton survived with just a broken ankle and injured shoulder.

Investigators said they have conducted an initial interview with Holton but want to talk with him more after he makes a full recovery.

NTSB investigators will also take a closer look at the weather at the time of the crash to see what role it played. A final report on a cause of the crash may take up to a year to be released.