The crash, near Victory Boulevard and just west of the 5 Freeway, was reported shortly before 1 a.m., according to officials from the California Highway Patrol.
Authorities said an SUV hit a center divider and when emergency crews arrived, there was a body on the road.
Investigators were trying to determine if the person killed was the driver or a pedestrian.
A SigAlert was issued for all eastbound and westbound lanes of the 134 Freeway overnight, according to the CHP.
Around 2 a.m., two lanes on the westbound 134 Freeway were reopened, and all eastbound lanes were reopened just after 6 a.m.
5:47 AM SIGALERT UPDATE: SR-134 WEST OF I-5 ALL EB LNS OPEN - WB #1,2 LNS REMAIN CLOSED UNTIL FURTHER NOTICE FOR CENTER DIVIDER REPAIR WORK— CHP Southern Div. (@CHPsouthern) July 2, 2016
The crash remained under investigation.