Three other people were critically injured in the two-vehicle collision in Lancaster.
The crash occurred when one of the vehicles apparently ran a stop sign on a rural desert road and broadsided the other, sending both into a ditch, Los Angeles County Fire Department Inspector Tony Akins told KNBC-TV in Los Angeles.
Two of the people killed were not wearing seat belts, Akins added.
It was unclear Sunday which vehicle hit the other. Akins said the only witnesses were the occupants