The California Highway Patrol and Cal Fire have responded to a rollover accident on northbound Highway 101 north of Avila Beach Drive that's backing traffic up to San Luis Obispo.
A Cal Fire spokeswoman said that a truck equipped with a travel trailer flipped over and struck another truck at about 10:57 a.m., though the cause of the accident was not immediately known.
The agency did not immediately have information about injuries but said two ambulances were initially called to the scene and one was called off.
Two Cal Fire engines responded to the scene.
Northbound traffic remained backed up as of 11:30 a.m.