The chain-reaction crash on Interstate 5 that left three people dead and damaged a vital portion of the north-south artery late Friday was apparently set in motion when a trucker hauling a load of coffee beans and other goods emerged from a tunnel and lost control of his vehicle on wet pavement, slamming into a guardrail, sources with knowledge of the investigation said Tuesday.
The truck came to rest about a third of a mile south of the tunnel. The force of the crash, which occurred shortly before 11 p.m., caused the truck's engine block to fly over the guardrail and into the northbound freeway lanes. Other debris from the big rig littered the southbound lanes.
The sight of the disabled truck -- which caught fire -- apparently caused other drivers on the rain-slicked roadway to slow down, sources said.
For several minutes after the initial accident truckers successfully avoided additional collisions, the sources said. But eventually, sources believe, the sudden slowing triggered a pileup in the 550-foot tunnel just to the north of the original crash.
It does not appear any other vehicles struck the coffee bean hauler, and sources said a witness reported seeing the trucker immediately behind the initial accident come to a stop without incident.
California Highway Patrol officials refused to comment on what might have caused the 31-vehicle pileup near Santa Clarita or on any other aspect of their probe.
"We're not going to compromise our investigation," CHP Sgt. Mark Garrett said.
In the aftermath of Friday's pileup, truckers voiced concern about the configuration of the 1970s-era I-5 tunnel where most of the accident, and all of the fatalities, occurred. They complained that the stretch of road mixes three of the problems they dread most -- darkness, blind spots and curves.
It's difficult, they said, for truckers entering the tunnel to know what hazards might lie ahead on the other side.
Rain and wet pavement might also have contributed to the accident, experts said.
The pileup sparked a devastating inferno inside the tunnel, generating intense heat estimated at up to 1,500 degrees. Many of the vehicles involved were reduced to bits of scrap metal. Caltrans authorities said repair work on the tunnel could take months.
The driver of the coffee-bean truck, whose name has not been released, sustained minor injuries. He was treated at a local hospital and released hours after the accident, according to a source who asked not to be identified because he was not authorized to talk about the ongoing investigation.
The driver worked for Saia, Inc., a nationwide trucking company, which transports a wide variety of goods to market.
Spokeswoman Sally Buchholz acknowledged that one Saia vehicle was involved in the crash and said the company was "in the process of gathering information regarding this accident and are cooperating fully with the CHP."
"Saia would like to express our deepest sympathy and condolences to the families involved in the multiple-truck accident," Buchholz said. "Saia places great importance on transportation safety."
CHP Assistant Chief Warren A. Stanley said this week that a multi-disciplinary accident investigation team was collecting evidence, interviewing witnesses and, to the extent possible, assessing vehicle damage and roadway conditions.
Investigators, he said, faced significant challenges in trying to piece together the accident because much of the evidence burned.
Stanley said the investigation promised to be a huge undertaking that would generate thousands of pages of reports. He said he did not know when it would be completed.
"We're not going to give a time frame, because we are going to take our time," he said. "We're going to do it as expeditiously as possible, but we're going to be thorough."
Officials on Tuesday were still trying to confirm the identities of two men and a young boy who were killed in the fiery crash, said Lt. Fred Corral of the Los Angeles County coroner's office. Though family members have tentatively identified the deceased, Corral said investigators were seeking dental records to make positive identifications.
CHP officials, meanwhile, sought to clarify the status of a number of truck drivers involved in the wreck whom officials had earlier suggested were missing.
Garrett, the CHP spokesman, said investigators have contacted "most, if not all" of the drivers. But they have yet to match some of the drivers to trucks that were badly burned in the crash.
"Some of these vehicles were melted down to the ground, so it takes time," Garrett said. "But it's not as if these people have vanished into thin air. That was a miscommunication."