At least five people, including a motorcyclist, have died in a crash that shut down all lanes of the 10 Freeway for several hours at the Riverside Avenue offramp in Rialto after a semi-truck crashed through the center divider and caught fire, authorities said.

CHP officers investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

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A truck driver stuck in traffic looks at the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

***Graphic content*** Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)



Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Onlookers and drivers look at the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

San Bernardino County firefighters and tow truck drivers work together to remove a six-axle cement mover from the top of a car at the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Westbound traffic is backed up for miles on the I-10 after a five-person fatal wreck in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

San Bernardino County firefighters and tow truck drivers work together to remove a six-axle cement mover from the top of a car at the scene of a five-person fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)



***Graphic content*** Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

People stand on the roof of a taco restaurant to get a better look at a five-fatal accident scene on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

CHP officers investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

CHP officers look over the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Emergency personnel remove two bodies from a car that was crushed under a six-axle cement mover after a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)



Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Caltrans workers wait for the OK to repair the center divider from investigators on the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

CHP officers investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

Emergency personnel remove two bodies from a car that was crushed under the six-axle cement mover after a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

San Bernardino County firefighters and tow truck drivers work together to remove a six-axle cement mover from the top of a car at the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)



***Graphic Content*** Emergency personnel investigate the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

San Bernardino County firefighters and tow truck drivers work together to remove a six-axle cement mover from the top of a car at the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. February 16, 2018 (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

A CHP officer investigates the scene of a five-fatal accident on the Eastbound I-10 at the bottom of the Riverside Avenue offramp Friday in Rialto, CA. (TERRY PIERSON,THE PRESS-ENTERPRISE/SCNG)

“It’s one of the most horrific collisions I’ve seen in my 10-year career,” said Steve Carapia, a California Highwasy Patrol spokesman.

Just before 1 p.m. Friday, a six-axle cement pump truck was traveling west when for unknown reasons it crashed through the metal guardrail, entered the eastbound lanes and struck five other vehicles, according to Carapia.

The driver of the cement pump truck, who was alone in the vehicle, was taken to a local hospital with non-life threatening injuries, Carapia said. No one else required hospitalization.

The truck had come to rest atop multiple vehicles — and then some caught fire, CHP Officer Brian Alvarez said.

One of the vehicles hit by the cement pumper was a dump truck, however the driver of that vehicle was not injured, Carapia said.

As work continued Friday night to clear the wreckage, some of which had been under the cement pumper, CHP investigators believed they had found all the victims, Carapia said.

Albert Fuentes, 26, works at a junkyard near the freeway and said he heard two “boom” sounds when the accident happened.

“Then you see all this smoke,” he added.

SigAlerts posted after the crash initially announced the closure of eastbound lanes for eight to 10 hours and westbound lanes for three. Two westbound lanes were reopened by 5 p.m. But the eastbound lanes may remain closed until sometime during the daylight hours Saturday morning, Carapia said Friday night.

“We want to be methodical and have enough time to investigate this accident,” Carapia said of shutting the freeway shut down.

Not only does the guardrail need to be repaired, and wreckage cleaned up, but Caltrans will need to do an assessment of the highway “to make sure it hasn’t been compromised” by the crashes, he said.

Alvarez asked motorists to take either the 60 Freeway to the south or the 210 Freeway to the north as an alternate route.

The investigation into what caused the cement pumper to veer left and crash is ongoing, he said.

Christian Andujo was one of several drivers on Slover Avenue near the Riverside Avenue interchange unaware of the fatal crash.

“We’ve been trying to get on the freeway for an hour,” he said at around 3:15 p.m.

Mario Padilla said he had to stop at a Chevron gas station nearby to put water in his engine; his pickup truck was overheating while stuck on Slover Avenue — which runs parallel to the 10 Freeway.

In their desperation to escape the crash-related gridlock, a number of motorists chose to drive on Slover Avenue where, in some areas, the pavement ends, weaving through large rocks placed as a barrier to loose sand.

As a result, about six cars got stuck in the sand, but good Samaritans with four-wheel-drive vehicles pulled them out, Colton police Sgt. Ray Mendez said.

As a result, Mendez said he stationed a police vehicle with flashing lights in the area at about 6 p.m.

“That seemed to take care of the problem,” he said.

What made matters worse was a jackknifed semi-truck on the westbound 10 in Redlands flipped over near Tennessee Street that caught fire, CHP logs show. A SigAlert was called just after 3 p.m. and two lanes were closed, but were reopened Friday night.

Sixth Street in Redlands was also congested, with westbound 10 Freeway drivers exiting there from the Rialto crash.

The crash also is delaying public transportation in neighboring communities. Omnitrans announced just after 3 p.m. that Route 290 trips were 30 minutes down.

Kevin Lacy, San Bernardino County Sheriff-Coroner commander, is asking family members who think they may have lost a loved one in the crash to call 909-387-2311 or visit 175 S. Lena Rd. in San Bernardino.

Staff writers Sarah Batcha, Imran Ghori, Joseph Nelson, Jim Steinberg and Brian Whitehead contributed to this report.

This story is developing. Check back for updates.