A Los Angeles County firefighter walks toward burning wreckage in the truck route tunnel on southbound Interstate 5. Sources say the initial incident apparently involved a truck that was already about a third of a mile beyond the passageway. After several minutes, slowing traffic led to a chain-reaction pileup reports the Los Angeles Times.

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.

Read it here: I-5 May have Started outside Tunnel