A commuter van from NASA's Jet Propulsion Laboratory (search) tumbled 200 feet off a twisting mountain road Wednesday, killing three people and injuring seven, at least four of them seriously, authorities said.

The van was carrying 10 people to work at the laboratory when it plunged off the Angeles Crest Highway (search) in the Angeles National Forest (search) at about 6:30 a.m. and rolled down the mountainside, Los Angeles County Fire Department inspector Ron Haralson said.

"One person was able to get out of the van and make his way up to the road" to get help, Haralson said.

The van was carrying six employees of the lab in Pasadena, two contractors and two NASA employees, said Blaine Baggett, a JPL spokesman. Their names were not immediately released.

"It's a very, very sad day for all of us at JPL," Baggett said, adding that employees will be offered grief counseling.

Three people were pronounced dead at the scene. One person was flung from the van. Others lay trapped in the battered white van in the middle of a dense forest until firefighters arrived.

Firefighters tore off the doors to reach victims, who were taken by helicopter to hospitals.

Of the survivors, one person was in critical condition, three were in serious condition, two had minor injuries and one person was still being evaluated, Haralson said.

The cause of the accident was not immediately known. Clouds and fog shrouded the site, at an altitude of about 1,500 feet. Snow dotted flanks of the mountain, but the road itself was clear.

Hundreds of cars a day travel the highway, a twisting, two-lane blacktop with steep drops. Commuters living in the Antelope Valley (search) area northeast of Los Angeles use it as a shortcut to reach a freeway in Pasadena.

JPL is the control center for several NASA projects, including the Mars rovers.

About 450 of the 5,500 people who work there participate in its vanpool program, which involves about 30 vans, Baggett said.