A single-engine airplane crashed and exploded in foothills northwest of Boulder, killing the only person on board, a sheriff's spokesman said Saturday.

The four-seat Cessna 180 went down on a hillside before 4 p.m., Boulder County Sheriff's Supervisor Jay Willette said.

The pilot's name was not immediately available.

The site is inaccessible to vehicles, and rescuers had to walk two miles to the debris. The fire was out by the time the first rescuers arrived, Willette said.

He did not know where the flight originated or where it was headed.

Kimberly Kenyon, a Federal Aviation Administration air traffic controller at the Jefferson County Airport, said winds were strong in the area Saturday afternoon, gusting up to 50 mph.

Federal Aviation Administration investigators and the National Transportation Safety Board were en route to the site, Willette said.