Three lanes of the northbound 5 Freeway near Castaic were closed Wednesday morning following a traffic incident involving a tanker truck, the California Highway Patrol said.
The accident was reported around 4:47 a.m. near Lake Hughes Road, the CHP said. It was not immediately known what led to the collision involving the 26,000-pound truck.
CHP officials said diesel fuel on the road prompted the closure of the freeway lanes, and that an onramp was also closed for several minutes.
One lane of the roadway remains open to motorists, causing traffic to back up for many miles.
Authorities did not have an estimate of when the other lanes will reopen.