The southbound 5 Freeway near Gorman became a mangled mess around 3 p.m. when two separate crashes occurred shortly after each other that led to a chain reaction. Authorities initially said up to 50 vehicles were involved in the pileup with as many as 100 vehicles trapped in between the two crash locations.
The southbound lanes were shut down shortly after.
Videos of the scene showed at least one car in flames, sending black smoke billowing into the sky. Several vehicles were severely damaged and others flipped over.
"Suddenly, I just saw a car stop for no reason and then we all got into an accident," Raul Macias, who was involved in the pileup, told KABC.
A child was taken to the hospital in critical condition, KTLA reported. Another 11 people were hospitalized with moderate to minor injuries.
At least 22 people were also injured but declined to be taken to the hospital.
A horse in a trailer died and two other horses were rescued from the scene.
Officials reopened 5 Freeway just before 7 p.m. Saturday. The exact cause of the crash was not released, although thick fog and poor visibility may have contributed to the incident.