An apparent mudslide has blocked two lanes on northbound Interstate 280 at Farm Hill Boulevard, south of Redwood City, according to the California Highway Patrol.

First reported shortly before 3:30 p.m. Sunday, the slide initially blocked all four lanes on the freeway and reportedly hit some vehicles with rocks.

The two right lanes remain closed for cleanup, and officials estimate could be 1 to 2 hours before all lanes are reopened. Drivers are being told to avoid the area.