The flames abated in a freeway tunnel Saturday where more than a dozen big-rig trucks lost control in the rain, causing a fiery pileup that injured at least 10 people and left one missing, but authorities still couldn't enter it to determine whether anyone died. The key route connecting Los Angeles and San Francisco remained blocked and was still smoldering more than 14 hours after the wreck. "It looked like a bomb went off," said Los Angeles County firefighter Scott Clark, who battled the blaze throughout the night.

The accident, which left wreckage scattered for at least half a mile, began when two trucks collided about 11 p.m. Friday in a southbound truck tunnel on Interstate 5 about 30 miles north of downtown Los Angeles, said Fire Inspector Jason Hurd.

The crash triggered a pileup involving about 15 big rigs and possibly one or more passenger cars, sending people fleeing for their lives. At least five trucks burst into flames, and the fire spread to the others.

Flames shot out of both ends of the tunnel, rising as high as 100 feet into the air, according to firefighters at the scene.

The tunnel, about an eighth of a mile long, offers trucks a more direct route on a web of canyon highways that also thread traffic on other levels.

The intense heat caused concrete to crack and melt, sending chucks falling onto a road below the tunnel throughout the night. Firefighters worried the damage could cause parts of the tunnel to collapse, particularly if they allowed many cars back onto the road that runs above it.

"The tunnel may be structurally compromised, so we're fighting the fire from outside right now," Deputy Chief John Tripp told KABC-TV.

Most of the flames appeared to have been extinguished by Saturday afternoon, but thick columns of smoke were still curling out of the tunnel and into surrounding canyons. Firefighters poured flame retardant into one end of the tunnel to douse any hot spots.

Until they could go inside, they said, they wouldn't know exactly how many vehicles were inside and whether any of the big rigs were carrying toxic chemicals.

The highway is also a major commuter link connecting Los Angeles to its northern suburbs. There are likely to be huge traffic jams in the area if it is still closed when people return to work on Monday.

The charred skeletons of at least a half-dozen big rigs could been seen peeking out of the tunnel's south end. At least one was carrying produce, and a smoldering load of cabbages lay scattered across the pavement.

Hurd said 20 people fled the fiery tunnel on foot, including the 10 injured. Eight were reported to have minor injuries, and two had moderate injuries. All were taken to hospitals and treated mainly for burns and neck and back injuries.

One truck driver was unaccounted for, and authorities were worried that more people may be missing.

"At this point we haven't confirmed any fatalities," said California Highway Patrol spokesman Rick Quintero.

Although the tunnel is designed to carry truck traffic through a mountain pass area, passenger cars may also use it, raising concerns that some may be trapped inside, Hurd said.

"We're going to have to do a very methodical search," Tripp said. "There could be, unfortunately, more people that were not able to escape."

Hurd couldn't say when authorities might be able to reopen the section of freeway.

"It could be another day, it could be days, it could be weeks," he told The Associated Press.

State transportation engineers were trying Saturday to determine when firefighters and rescue workers could enter to douse the remaining flames and look for anyone who might have been trapped.

The section of freeway was shut down twice before, by earthquakes in 1971 and 1994, when large overpasses over canyons collapsed. The worst of the temblors, the Northridge quake of 1994, also damaged another nearby highway, snarling traffic throughout the area.

Written By NOAKI SCHWARTZ