The 14-vehicle chain-reaction pileup occurred about 9 a.m. at Oak Hill Road and left most of the victims with moderate to minor injuries, according to the county fire department, which performed triage at the crash site.
The majority of the patients declined to be transported to a hospital, according to fire officials. Two were taken to a medical center with unspecified injuries.
Heavy fog, reduced visibility and speed were believed to be contributing factors to the collision, which began when a vehicle spun out and others swerved in an attempt to avoid it, investigators said. Visibility was poor in the area due to heavy fog.
Heavy fog in the #CajonPass was a contributing factor to a chain reaction crash that has all southbound lanes of the I-15 shutdown. CHP says as many as 20-25 vehicles involved. Mostly minor to mod injuries. Stay tuned to @ABC7 for more updates. pic.twitter.com/HcKDsHpuL5— Leticia Juarez (@ABC7Leticia) January 16, 2019
A miles-long backup of traffic ensued as California Highway Patrol and Caltrans personnel worked to clear the roadway. Several cars and at least three big rigs were heavily damaged in the wreck.
Drivers stuck in the mess were frustrated.
"It's bad," said Compton resident Antwon Long. "I'm going to keep it real with you all -- I drove on the side of the freeway to get right here."
Just eight months ago, there was a chain-reaction wreck that shut down the Cajon Pass after two cars spun out.
"It was really foggy and everything, but I didn't think this would happen again. I thought people would learn their lesson from last time," shared driver Mitch Robinson.
It was deja vu all over again for many drivers as CHP, Caltrans and tow trucks worked to clear the road and reopen the highway.
All lanes were reopened about 12 p.m., Caltrans said.