A woman was killed and four others -- including three children -- were critically injured after a vehicle fell 100 feet over the side of the road on the southbound 5 Freeway near Castaic on Sunday afternoon, authorities said.
Around 2:30 p.m., the California Highway Patrol received a report that a vehicle had gone off the roadway at the Islands, according to CHP Officer Patrick Kimball.
The car, for reasons unknown, lost control and veered to the right onto an embankment where it began to overturn, CHP Officer Robert Crenshaw said.
The cause of the crash was under investigation.
All three juveniles were rushed to Children's Hospital Los Angeles where they were last reported to be in critical condition. The adult male -- also said to be in critical condition -- was taken to a hospital in Newhall.
It was not immediately clear whether the woman who was killed and the critically injured man and three children were related to one another. Authorities have not released the names of any of the victims.
Following the crash, CHP issued a SigAlert and shut down the No. 4 lane of the southbound roadway. The closure was initially expected to last for roughly three hours, according to the agency's incident log.
But it remained closes long after the roadway was expected to reopen, leaving southbound traffic snarled in the area for some 5 to 7 miles by 6 p.m.
The alert was canceled at about 8 p.m., according to CHP.
KTLA's Feven Kiflegiorgis contributed to this story.