The Sacramento Bee reports a Ford Expedition carrying nine people was going southbound on the highway Sunday when it veered out of control and crossed the center divider, colliding with a Honda Accord heading north.
Both cars flipped and people were thrown from both vehicles.
The driver and two passengers in the Ford, and the driver of the Accord were killed. All of the injured were taken to hospitals. Their conditions were not immediately known.
The California Highway Patrol shut the northbound lanes for several hours to investigate, causing traffic to back up for miles.