405 Freeway SigAlert in West Los Angeles causes major traffic backup

Two cars overturned on Los Angeles’ 405 Freeway during the Thursday morning rush hour, closing several northbound lanes and triggering a major traffic backup.

The crash was reported shortly before 7:30 a.m. near Santa Monica Boulevard, according to the California Highway Patrol (CHP).

At least one person involved in the crash declined to be taken to a hospital, CHP reported. It was not immediately clear whether anyone suffered serious injuries.

The overturned cars blocked lanes as emergency crews responded to the scene. Video from KTLA showed traffic stacking up behind the crash as some drivers caught in the growing backup attempted to exit the freeway.

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CHP issued a SigAlert shortly after 8 a.m. for the closure of lanes 4, 5 and 6 as crews worked to clear the wreckage.

Under CHP policy, SigAlerts are issued for unplanned events or circumstances that could delay a large number of motorists for at least 30 minutes. Traffic collisions, spilled loads, flooding and unexpected congestion are among the situations that can trigger an alert.

The agency extended the SigAlert for another 30 minutes at about 8:30 a.m.

The collision occurred on northbound I-405 near Santa Monica Boulevard in West Los Angeles. The freeway continues north from the Westwood area toward the Sepulveda Pass.

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Caltrans has previously directed motorists seeking an alternate northbound route from Santa Monica Boulevard to travel east to Sepulveda Boulevard before continuing north to an I-405 entrance at Moraga Drive.

The lanes affected by Thursday morning’s crash were eventually cleared and reopened.

The cause of the crash was not immediately clear, and authorities had not announced whether any citations or arrests resulted from the collision.

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Fox News Digital reached out to the California Highway Patrol for additional information but did not immediately receive a response.