RUNNING SPRINGS, Calif. (AP) — A bus carrying teenagers back from a camp overturned on a twisting mountain road in Southern California, resulting in 20 people being hospitalized, with three sustaining serious injuries, officials reported on Monday.

The accident occurred around 9 p.m. on Sunday as the bus, carrying 36 passengers, navigated a curve on State Route 330 near Running Springs, situated approximately 70 miles northeast of Los Angeles, according to the San Bernardino County Fire Department.

Upon arrival, first responders discovered the bus lying on its side, with passengers making their exit through a hatch on the roof, as indicated in a statement from the fire department.

“A total of 26 individuals were treated, including three with severe injuries. Out of these, 20 were taken to nearby hospitals via ground ambulances,” the statement detailed.

Photographs released by the fire department depicted victims sitting on the ground in a designated triage area, some of them fitted with neck braces for support.

The bus, carrying adults and teens, was traveling downhill back to Orange County from a camp near the tiny community of Angelus Oaks in the San Bernardino Mountains, officials said.

There was no fire or hazardous material exposure, the fire department said.

State Route 330 is a two-line highway where it curves through forest areas near Running Springs at an elevation of about 6,100 feet (1,860 meters).

The route was closed in both directions during the investigation, which was led by the California Highway Patrol.