A big rig spilled about 150 gallons of diesel fuel on the 5 Freeway in Newhall late Friday, forcing the closure of all southbound lanes, authorities said.
The fuel spill was reported about 8:40 p.m., said California Highway Patrol Officer Anthony Polizzi. By 9 p.m., the freeway's southbound lanes were shutdown.
Officers were diverting vehicles at the Lyons Avenue exit and allowing traffic back on the freeway at the Calgrove Boulevard on-ramp.
Although a cleanup is underway, authorities had no estimate on when the freeway would reopen.
Traffic in the area is backed up for miles.