A bus carrying teenagers and adults returning from a church youth retreat overturned Sunday night on a winding mountain road in Southern California, leaving 20 people hospitalized, three of them with serious injuries, authorities confirmed Monday.

The crash occurred on a sharp curve along State Route 330 near Running Springs, approximately 70 miles northeast of Los Angeles, according to the San Bernardino County Fire Department. The vehicle, carrying 36 passengers from Our Lady of Guadalupe Catholic Church in Santa Ana, had been descending from Camp Nawakwa in the San Bernardino Mountains when it lost control and rolled onto its side.

Emergency crews arrived to find the bus tipped over, with several passengers climbing out through a roof hatch. “A total of 26 patients, including three with major injuries, were treated at the scene. Twenty were transported to nearby hospitals,” the fire department reported.

Photographs released by officials showed paramedics assisting several victims wearing neck braces as a triage zone was established on the roadside. Authorities confirmed there was no fire or hazardous material threat following the crash.

Jarryd Gonzales, a spokesperson for the Diocese of Orange, said the group had just concluded a three-day retreat involving about 125 participants—teens, volunteers, and staff—traveling in several vans and the ill-fated bus. “We extend our deepest gratitude to the first responders for their swift and professional efforts,” Gonzales said.

State Route 330, a narrow two-lane highway that winds through steep forested terrain at around 6,100 feet elevation, remained closed in both directions while the California Highway Patrol investigated the cause of the accident.

No fatalities were reported.