At a Glance

At least 20 vehicles were involved in a pileup in Southern California's Cajon Pass Wednesday morning.The collision left at least 17 people injured.Officials said dense fog was present in the area at the time of the crash.

At least 17 injuries were reported in a 20-car pileup Wednesday morning along Interstate 15's southbound lanes in the Cajon Pass, Southern California authorities said.

The collision, which occurred just before 11 a.m. local time Wednesday morning, shut down the southbound lanes of the freeway , according to the San Bernardino County Fire Department. Reports say thick fog was present in the area at the time of the crash.

A follow-up tweet from the fire department from 27 to 17.

"Drivers likely drove from nearly clear skies into a thick bank of marine layer fog," said weather.com meteorologist . "This dense fog is being propelled inland by a weak low-pressure system located near Los Angeles."

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Video tweeted by a local reporter showed thick fog near the crash.

It wasn't immediately clear how serious any of the injuries were, but the San Bernardino County Fire Department said two of the injured were immediately transported to a nearby hospital.

The Cajon Pass is located about 60 miles northeast of Los Angeles.

This is a developing story; please check back frequently for more details.