Boulders tumbled from a hillside and landed on two unoccupied cars in the Sunset district Saturday morning, damaging both vehicles.
Officials say no one was injured in the incident at Quintara Street and 12th Avenue.
The incident forced the 6-Parnassus bus line to be rerouted and switch-backed buses at 14th Avenue and Noriega Street.
Quintara between Cragmont and 12th avenues is closed and people are asked to avoid the area. The Department of Emergency Management is continuing to monitor the situation.