RENO (Nevada) - THE pilot of a small plane that nose-dived into a northern Nevada cow pasture, killing all five people aboard, was making low passes over a party shortly before the crash, a federal investigator said on Sunday.

National Transportation Safety Board and Federal Aviation Administration investigators on Sunday combed the wreckage for clues as to whether human error, weather or a mechanical problem caused the crash a day before near Gardnerville, about 50 miles (80 kilometres) south of Reno.

Investigators were unable to examine the engines because both were buried in the ground, he said. They will be examined at a Sacramento, California, warehouse after the wreckage is removed from the site Monday.

NTSB investigator Van McKenny said witnesses told him that the pilot, Gary Annas, 58, of Minden, was making low passes over the party shortly after taking off from the nearby Minden Tahoe Airport when his twin-engine Beechcraft BE95 made a steep turn and crashed.

Mr Annas had earlier stopped by the party to ask if anyone wanted to accompany him on the flight that was to start and end at the airport, Mr McKenny said.

The crash occurred about 19 kilometres from the airport in the rural Carson Valley along the eastern base of the Sierra Nevada mountain range.

The passengers were identified as Paul Dallas, 43, of Minden; Leia Denner, 40, and Brent Fahey, 30, both of Gardnerville; and Beau McGrath, 30, of Kirkwood, California.

Witness Douglas Bradshaw, a former pilot, said the plane appeared to be flying normally at a relatively high speed before it crashed about metres from his house.

He said the plane passed about 60 metres over his home as he and his wife were sitting on the patio, then suddenly climbed, lost lift and spun into the ground.

Investigators also have requested Air Traffic Control and radar data, saying it could help provide clues. The small craft had no black box. -- AP