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.

Fire crews had the blaze out by 7 a.m. and remained at the scene monitoring hot spots well into the morning, authorities said.

It all started on westbound Interstate 580 about 4:45 a.m. and forced the closure of the freeway between Grant Line Road and Greenville Road. The CHP did not have all lanes of the freeway opened until 12:15 p.m.

According to the CHP, the 18-wheeler carried almonds, and something caused it to go ablaze. They were investigating how it happened. The wind in the area helped carry the flames into the hills, the CHP said.

The closure of all the westbound lanes lasted until 9:45 a.m., when the CHP opened the far left lane.

The CHP also closed the westbound I-580 on-ramp at Flynn Road.

Motorists were directed to use Altamont Pass Road and Corral Hollow Road to bypass the shutdown.

The fire did not cause any injuries, authorities said. Fire officials said it burned about 3 acres.