A bus carrying teenagers back from a camp overturned on a winding mountain road in Southern California, resulting in 20 hospitalizations, including three with serious injuries, authorities reported on Monday.

The accident occurred just before 9 p.m. on Sunday when the bus, carrying 36 individuals, crashed on a curve along State Route 330 near Running Springs. This area is approximately 70 miles northeast of Los Angeles, as noted by the San Bernardino County Fire Department.

Upon arrival, first responders discovered the bus lying on its side, with passengers making their escape through a hatch on the roof, according to a statement from the fire department.

“A total of 26 individuals received treatment, with three sustaining major injuries,” the statement disclosed. “Out of these, 20 were transported to local hospitals via ground ambulances.”

Images released by the fire department depicted victims seated on the ground in a designated triage area, some of whom were fitted with neck braces.

The bus was on its way downhill to Orange County from a camp situated near Angelus Oaks, a small community in the San Bernardino Mountains, officials confirmed.

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.