LIVERMORE — A fire that began on a big rig spread to a hillside near the Altamont Pass early Friday and forced an hourslong closure to one direction of a freeway that lasted into the afternoon, the California Highway Patrol said.

All lanes on westbound Interstate 580 at the Altamont Pass are blocked Friday morning after due to a vehicle fire.

An 18-wheeler caught fire Friday morning on Interstate 580, igniting a vegetation fire and forcing a full closure of the freeway’s westbound lanes in Alameda County, fire officials said.