A big-rig and nine other vehicles have crashed on Interstate 5 in the mountains north of Los Angeles.

California Highway Patrol Officer Scott Jobinger says Wednesday's crash occurred in foggy conditions shortly before 1 p.m.

Two people have been flown to hospitals and officials expect more injuries.

The crash was reported as a runaway truck striking the nine other vehicles on a stretch of downhill highway on the northern side of Tejon Pass, which rises to an elevation of more than 4,000 feet.

The crash has created a miles-long backup on the northbound side of I-5, one of California's major routes for travel and truck traffic.

Visibility was reported as low as 400 feet at the time of the accident.