The incident was reported about 11:30 p.m. near the 405 South's Roscoe Boulevard exit.
California Highway Patrol officials said a truck hit a pedestrian, and it was unclear why or how long the unidentified victim was on the freeway before the crash.
At about midnight, all lanes were shut down for about two hours at Roscoe Boulevard as officials investigated the scene.
It was not known whether anyone in the truck was injured.