Nearly all lanes of the southbound 405 Freeway were closed Monday night following a fatal hit-and-run collision in the West Los Angeles area.

The crash happened around 10:45 p.m. on the freeway near Santa Monica Boulevard, according to a California Highway Patrol news release.

A pedestrian seen running on the shoulder of the freeway was struck and declared dead at the scene, according to the CHP.

The deceased has not been identified and was only described as a 66-year-old man.

It was unclear why the man was running on the freeway.

Officers are searching for the vehicle involved in the crash, which may be a white Toyota sedan.

The incident resulted in the issuing of a SigAlert, which left nearly all lanes stopped and traffic moving at a crawl.

CHP officials told KTLA that all but one lane on southbound 405 were closed due to the fatal collision investigation.

Drivers were being diverted off of the freeway onto Santa Monica Boulevard due to the closure.

The SigAlert was canceled and the roadway cleared early Tuesday morning, the CHP tweeted.