California Highway Patrol Sgt. Brian Brown says the mudslide began at about 2 p.m. Wednesday in Sun Valley and may have been spurred by rain throughout the region.
Traffic is being diverted off of the northbound freeway at Glenoaks Boulevard. On the southbound side of I-5, vehicles are being directed to drive through the freeway's center divider.
Brown says it's unclear when the freeway will reopen because Caltrans will need to bring out equipment to clean up the mud.