A converted military plane crashed Saturday in heavy fog in the mountains that frame the Salt Lake valley, killing three members of a private firefighting company, authorities said.

Tooele County Sheriff Frank Park said the plane was en route from Missoula, Mont., to Alamogordo, N.M., when it failed to clear a pass in the Oquirrh Mountains.

The crew members for Missoula-based Neptune Aviation were bound for southern New Mexico to help fight a nearly 30-square-mile wildfire, said Dan Ware, a spokesman for the New Mexico Forestry Division.

"While we must pause to mourn their loss, within the wildland community we must also honor them by continuing to fight fires to protect our communities," state forester Arthur Blazer said.

The wildfire, which was 20 percent contained, was threatening a home and several outbuildings and a power distribution line, officials said.

The sheriff identified the pilot as Tom Risk, 66, of Littleton, Colo., and the crew members as Mike Flynn, 59, of Alamogordo, N. M., and Brian Buss, 32, of Alberton, Mont.

Neptune's ground safety and security coordinator, Miek Pfau, said he could confirm only that the company lost an aircraft.

The wreckage of the plane, a twin-propeller P2V Neptune with a 100-foot wing span, was located near Stockton Pass, spread out over about 100 yards, Park said.

Search and rescue crews reached the steep, rugged site on foot and all-terrain vehicles to recover the bodies. They were turned over to the state medical examiner, he said.

Investigators with the Federal Aviation Administration were at the crash site Saturday, and officials with the National Transportation Safety Board planned to arrive Sunday, the sheriff said.

Park said the Neptune, a plane developed during the Korean war that is commonly used to fight wildfires, had been equipped for dropping fire retardant.

He said visibility was only 100 feet when the plane failed to clear Stockton Pass. It missed the pass by an eighth of a mile and slammed into a mountain instead, but should have been flying higher, he said.

The plane was being tracked by the National Interagency Fire Center in Boise, which lost track of it before the pilot could report any trouble or issue a distress signal, the sheriff said.