Multiple vehicles have collided in dense fog on Interstate 15 in Cajon Pass about 60 miles east of Los Angeles and initial reports say at least 17 people have been hurt.
California Department of Transportation district spokeswoman Terri Kasinga says the number of vehicles in the pileup late Wednesday morning is unknown but may involve as many as 20.
The San Bernardino County Fire Department tweets that two patients were transported immediately and 15 others had minor injuries. Numerous drivers and vehicle occupants declined treatment.
The pass runs between the San Bernardino and San Gabriel Mountains and rises to an elevation of nearly 3,800 feet.
Southern California is experiencing a deep intrusion of marine air that has brought low clouds, fog and rain.