At least eight people have been killed after a tour bus collided with two other vehicles in the mountains of southern California.
Police said as many as 10 people may have been killed in the smash.
Another 38 people were taken to hospital with injuries after the crash about 80 miles east of Los Angeles near the town of Forest Falls, California Highway Patrol spokesman Mario Lopez said.
The bus driver reported having brake problems as the vehicle came down the mountain on State Route 38, Mr Lopez said.
It crashed into a car before flipping over and hitting a pick-up truck that was pulling a trailer.
A spokeswoman for the US Department of Transportation said the passengers on the bus were part of a tour group from Tijuana, Mexico.
Describing the grim crash scene, she said: "It's really a mess up there with body parts."
A representative from the Mexican consulate was present, she added.
Jordi Garcia, a manager for InterBus Tours, said his company ran Sunday's trip, which departed Tijuana at 5 am for a day of skiing at Big Bear Lake, a popular mountain resort northeast of San Bernardino.
At least seven ambulances were called to the scene and the injured are being treated at several hospitals in the area.
Fifteen of them are reported to be in a critical condition, reports said.
Lettering on the bus indicated that it was operated by Scapadas Magicas, a company based in National City, California.
Federal transport records show that the company is licensed to carry passenger for interstate travel and that it has had no crashes in the past two years. Calls to the company were not returned.
The California crash comes less than a day after a bus carrying 42 high school students and their chaperones slammed into an overpass in Boston. Some 35 people were injured.