GORMAN (CBS/AP) — At least 100 cars were trapped on southbound Interstate 5 near the Grapevine, after 2 massive crashes involving several dozen cars, Saturday afternoon.

At least 12 people were sent to the hospital, four people were critically injured, including a toddler, according to authorities.

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The crash happened around 3 p.m. The Grapevine section of the interstate was closed for hours as emergency crews responded to the accidents. The road was reopened around 7:30 p.m.

The California Highway Patrol’s traffic incident website said the accidents occurred amid thick fog.

“Southbound I-5 is closed at Frazier Mountain Park Road due to multiple vehicle collisions involving injuries,” said the CHP in a post on Facebook around 4 p.m. “Traffic is being diverted to surface streets causing major delays. If you are heading southbound, now would be a good time to check out the The Outlets At Tejon.?”

The pileups involved as many as 50 vehicles and have trapped 100 cars in-between.

Photos shared across social media showed one car was overturned, and thick black smoke billowing from another car on fire. Video shared on Twitter shows traffic at a standstill.

A horse was killed in the crash.

Paramedic helicopters flew in to assist from as far as Kern County.

The Grapevine carries traffic over mountains between greater Los Angeles and the San Joaquin Valley. The wrecks caused traffic on northbound and southbound lanes to back up for miles.

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