The 405 South reopened in Orange County hours after a fatal crash in the Huntington Beach area on Saturday morning.
Two people died and four others were injured after a multivehicle collision around 4 a.m. near Beach Boulevard, according to California Highway Patrol.
A male driver believed to have been impaired was traveling at high speed when his black Honda struck a pickup truck, CHP Officer Duane Graham told KTLA.
When the Honda came to a stop, another vehicle hit it head-on, investigators said. Two other motorists became involved in the crash, authorities added.
Two people, including the driver of the Honda, were hospitalized with major injuries, Graham said.
Footage from the scene shows debris strewn across the road as several cars involved in the incident remained on the freeway. A pickup truck was seen behind bushes on the side of the road.
Authorities shut down the the southbound lanes north of Beach Boulevard and were diverting motorists off the freeway at Goldenwest Street, Caltrans said.
The closure was expected to last for "the next couple hours," the agency said at 5:24 a.m. Shortly after 10 a.m., Caltrans tweeted that all lanes were reopened.
Authorities provided no further information.