GREENVILLE, Maine — A Massachusetts pilot was warming his plane’s engine in flight Saturday morning when the aircraft crashed for unknown reasons, killing him, federal investigators have learned.

“He took off from the airport to warm up the engine, to warm the oil, prior to an oil change,” National Transportation Safety Board spokesman Peter Knudson said Monday morning.

David Finnegan of Woburn, Mass., took off from Greenville Municipal Airport at about 8:15 a.m. Saturday.

“Several witnesses reported seeing the aircraft maneuvering at a low altitude, then reported seeing the airplane nose down and disappear from sight,” Knudson said.

The small Cessna 172M crashed in a heavily wooded area about a mile and a half from the airport. Finnegan, whose age wasn’t immediately available, was the only person aboard.

Greenville police and fire responded and, with the assistance of the Maine Department of Inland Fisheries and Wildlife and game wardens, found the plane shortly afterward near the Eagle Stream Road, Greenville police Chief Jeffrey Pomerleau said Sunday.

“Mr. Finnegan was pronounced dead at the scene,” he said.

There was no fiery explosion, Knudson said.

He said Todd Gunther, an air safety investigator based at the NTSB office in Ashburn, Va., arrived late Saturday to begin the sifting through the wreckage.

“We’re in the process of reclaiming that wreckage, removing it, today,” Knudson said Monday.

Gunther is expected to remain in the Greenville area investigating the plane crash until Wednesday, and the preliminary report about his findings is expected to be finished next week. It will lay out the facts that are known, Knudson said.

How long Finnegan had been a pilot, his license rating and medical records, and the Cessna’s maintenance record will be part of the investigation, along with a look into Finnegan’s actions in the 72 hours before the crash, he said.

“There is a whole host of things we’re going to be taking a look at,” Knudson said.