The collision, involving a Ford Mustang and Chevy Camaro, happened shortly after 3 a.m. near El Segundo Boulevard, according to the California Highway Patrol.
Officers and firefighter-paramedics arrived at the scene to find both vehicles on their sides, a CHP incident log said.
An unconscious male was transported to a hospital after being found unconscious inside the Mustang, the Highway Patrol said.
All northbound traffic was being diverted from the 405 to the 105 Freeway as crews worked to clear the two cars from the crash site.
DEVELOPING: More details will be added to this report as they become available.