A U.S. Forest Service transport van plunged 400 feet off a road in the San Bernardino Mountains on Monday, injuring the eight firefighters inside, a Forest Service spokesman said.

Six of the firefighters suffered minor injuries and were taken by ambulance to a local hospital, while two suffered moderate injuries and were flown to a regional medical center, said John Miller, the spokesman.

Miller did not know the nature of the crew's injuries. He said the firefighters belonged to a hand crew working on mopping up the Butler 2 Fire, which was fully contained recently.

A Forest Service dispatcher said the crew was supporting a helicopter that was working the fire.

Some of the crew members had broken bones, including one person who had a possible broken pelvis, said Andrea Lannen, the dispatcher. That person was being transported to Arrowhead Regional Medical Center, while others were being taken to Bear Valley Community Hospital, she said.

"So far, there's a lot of broken bones," she said.

The accident happened just before 10 a.m. and the road was dry and clear. There were some clouds overhead, Miller said. The cause of the accident was being investigated by the California Highway Patrol.

Highway 18 was closed between Running Springs and Big Bear Lake until 2 p.m. so rescue crews could operate, Miller said.

The Butler 2 Fire began on Sept. 14 and burned more than 14,000 acres and three outbuildings before it was fully contained about a week later. The blaze also briefly forced the evacuation of the rural township of Fawnskin.

Crews are now working to put out the fire within the containment lines, Miller said.