A big rig carrying rice, sushi and other food caught fire while coming off the Bay Bridge on Monday morning, a blaze that kept three lanes of westbound Interstate 80 skyway in downtown San Francisco closed into the afternoon.

The three right lanes remained shut down at 3 p.m. while fire investigators examined the charred wreckage and crews removed the truck from the freeway.

"I've been told it's still a mess up there," said Officer Mike Ferguson, a spokesman for the California Highway Patrol.

The truck driver pulled to the side of the road with a flat tire at 5:45 a.m. and realized that his engine was on fire, said CHP Sgt. Laura Clare.

The driver jumped out of his cab and ran away from the truck, which eventually became fully engulfed in flames, Clare said. He was not injured.

The driver was hauling groceries from Castro Valley to South San Francisco, Clare said. Ferguson said the truck was full of sushi, rice, vinegar, dressing and other food.

The truck and all the food was destroyed.

Commuters were lucky a BART strike was headed off late Sunday, because thousands of additional cars would have been stuck on the bridge and its approaches if there had been no train service, said CHP Officer Kevin Bartlett.

"That would have kind of perfect timing for it," Bartlett said. "Perfect in bizarro world."