SANTA CLARITA, California (CNN) -- Firefighters have made it about 50 feet inside the interstate tunnel north of Los Angeles where two people died in a massive fire that erupted from an apparent big-rig collision Friday night, California officials said Saturday.
Teams have been moving into the tunnel 10 feet at a time to assess its structural integrity and safety, said John Tripp, deputy chief of the Los Angeles County Fire Department.
Debris is hampering the efforts, but officials hope to end the search operations by Sunday evening.
The fire burned "very intensely" for up to four hours, Tripp said.
Winds whipped the flames from one end of the tunnel to the other, and the searing heat from the flames caused concrete inside the tunnel to explode, adding to the debris.
As of about 5 p.m. Saturday (8 p.m. ET), most of the flames were out, except for some wreckage that was still smoldering. Watch what firefighters were up against »
Earlier, firefighters shot high-expansion foam into the tunnel to try to smother the fire so crews could enter on rescue missions.
The incident on the southbound lanes of Interstate 5 happened at about 10:40 p.m. (1:40 a.m. ET) Friday, said Warren Stanley, assistant chief of the California Highway Patrol. See more photos of the inferno »
Five to six big rigs were in the 550-foot-long tunnel at the time, along with a number of passenger vehicles, he said. While the tunnel was described as trucks-only, authorities said cars are free to travel in the tunnel, in Newhall Pass between Santa Clarita and Los Angeles.
Since investigators have not been able to examine the whole of the wreckage and have yet to interview survivors, officials don't yet know what caused the collision or if the fire was sparked by one accident or several, Stanley said. The speed limit inside the tunnel is 55 mph.
"What's making this tough, obviously, is the fire burned so intense that a number of vehicles are burned down to the core," Stanley said.
Of the 10 people hurt in the accident, Tripp said eight had minor injuries and two had "moderate" injuries. The first engine company arriving at the scene after the initial calls was met not only by the fierce fire, but also by "a number of casualties self-evacuating and self-rescuing out of the tunnel," he said.
Authorities have not identified the two fatalities.
Officials said Saturday they hope to have the tunnel open to traffic by Tuesday morning, depending on when they can assess its structural safety.
California Gov. Arnold Schwarzenegger was monitoring the situation, said Will Kempton, director of the California Department of Transportation, or Caltrans. Schwarzenegger has put the state's emergency services on alert, he said, and the federal government has also offered assistance.
The structure is near the intersection of I-5, or Golden State Freeway, and California 14, or Antelope Valley Freeway. I-5 is the major north-south route in that part of the state. See a map of the interchange »
The blaze not only shut down the truck tunnel but also the northbound and southbound I-5 auto lanes that run above it. Authorities said a bridge above the tunnel that carries the two auto lanes also may be compromised.
"I-5 is a very important, major north-south route," Kempton said. "It's obviously very vital that we shoot to get this roadway open as soon as possible."
He and others asked for the public's patience as authorities determine the tunnel's safety for motorists.
The incident triggered delays of up to an hour Saturday, and officials are worried weekday traffic will be hopelessly snarled. They're urging motorists to find alternate routes and take advantage of public transit.
Caltrans is working with transit authorities to increase service in the area.
Kempton said 225,000 vehicles travel I-5 daily. According to 2005 data from Caltrans, the interstate carries 12,500 vehicles per hour at peak times of the day, and the annual average daily traffic is 164,500. E-mail to a friend
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