California Highway Patrol cruiser. Photo by Chris StoneA California Highway Patrol cruiser. (File photo by Chris Stone/Times of San Diego)

A big rig caught fire early Thursday on southbound Interstate 5, destroying six of the vehicles it was hauling and backing up traffic for roughly 12 hours.

California Highway Patrol officers responded to the fire shortly before 5 a.m. Thursday, according to the agency. The driver pulled over on the shoulder and escaped injury.

Caltrans closed several lanes of the freeway at the Aliso Creek Rest Area as first responders, including the Camp Pendleton Fire Department, dealt with the blaze.

While there were no injuries or other structural damage, all six vehicles “went up in flames,” according to CHP Officer Hunter Gerber.

Caltrans reopened the No. 2 and 3 lanes just after 3:30 p.m. Gerber said the No. 4 lane was reopened at 4:20 p.m.

Clean-up on that portion of the southbound I-5 took nearly 12 hours, due to the nature of moving the damaged vehicles off the trailer, along with cleaning up other debris. Traffic backed up into Orange County during the lengthy closure.

It was unclear what caused the trailer to catch fire.