Investigators are looking into whether the use of prescription medication was a factor in the crash.
A rollover crash killed a woman near Coalinga on Saturday morning.
It happened on Interstate 5 near Highway 145 just before 6 am.
The CHP says 46-year-old Lynda Williams was driving an Acura southbound when she drifted off the edge of the roadway and then overcorrected.
The car flipped over several times on the dirt shoulder.
Officers say Williams was not wearing a seatbelt. She was ejected and died at the scene.
A 10-year-old passenger was wearing a seatbelt and suffered only minor injuries.
Investigators are looking into whether the use of prescription medication was a factor in the crash.