YUCAIPA, Calif. — At least eight people were killed and 38 injured Sunday when a tour bus careened out of control while traveling down a Southern California mountain road, struck a car, flipped and plowed into a pickup truck, authorities said.

The accident occurred around 6:30 p.m. about 80 miles east of Los Angeles and left State Route 38 littered with debris, the bus sideways across the two lanes and its front end crushed. Emergency crews worked to free passengers who were trapped in the bus, which was returning to Tijuana, Mexico, said California Highway Patrol spokesman Mario Lopez.

The violence of the crash and severity of the injuries made for a chaotic scene, and authorities had a difficult time determining how many people were injured or killed. Lopez said at least eight and perhaps 10 were dead, and 38 transported to hospitals.