The crash happened on the outskirts of the town of Yucaipa

As many as eight people have been killed in California after a tour bus collided with two other vehicles on a mountain road.

Dozens of others are injured following the accident, which occurred near Yucaipa on the edges of the San Bernardino National Forest.

Officials at the scene said 27 people were taken to nearby hospitals, at least six of them in a critical condition.

The cause of the crash is not yet clear.

However, California Highway Patrol spokesman Mario Lopez told the Associated Press the bus driver reported brake problems as he descended a road leading from the Big Bear ski resort area.

The bus was in collision with a sedan car and a pick-up truck pulling a trailer, Lopez added.

The passengers were part of a tour group from Tijuana in Mexico.