17 Injured After Chain-Reaction Crash Involving 20 Vehicles in the Cajon Pass

All lanes were reopened in the Cajon Pass after a chain-reaction crash involving more than 20 vehicles Wednesday morning left at least 17 people injured and prompted a partial closure of the 15 Freeway for several hours, authorities said.

The multi-vehicle pileup occurred shortly after 10:40 a.m. on the southbound 15 Freeway north of Highway 138, according the California Highway Patrol.

Two people were transported with life-threatening injuries, Eric Sherwin of the San Bernardino County Fire Department told KTLA. Fifteen others received minor injuries, but it was not immediately clear how many were transported.

A number of others declined treatment; Sherwin indicated the initial patient count was as high as 27.

He said the patients were found over a two-mile stretch near Oak Hills.

Terri Kasinga of Caltrans described the crash scene as being in multiple areas of the roadway, with some vehicles overturned.

"It's kind of scattered," she said.

The incident occurred amid heavy fog in the area, with "extremely low visibility" of up to about 100 feet reported in the area, according to authorities. Fog was impacting the northbound lanes from Cleghorn to the top of pass.

"Traffic was just moving too quickly through there at the time of the accident," Kasinga said.

CHP has issued a SigAlert and all southbound lanes were shut down at Oak Hill for several hours. All lanes were reopened just before 1:30 p.m., Caltrans tweeted.

The crash and subsequent closure caused a major traffic jam in the area, with vehicles backed up to the area to at least Main Street in Hesperia as of 11:30 a.m., according to officials.

“It’s been a mess over the last couple of hours," Kasinga said.

Fog conditions were expected again Thursday, prompting authorities to issue a warning to motorists planning to travel through the area.

“Our best advice is for people to check traffic conditions before they come down through the pass," Kasinga said. “Basically slow down. Keep the distance in front of you and the car in front of you. And really, you’ve got to slow down.”

KTLA's Steve Bien and Jennifer Thang contributed to this story.