PUEBLO, Colo. (AP) — Colorado authorities on Monday were investigating what caused a bus carrying a New Mexico high school church group home from a weekend retreat to veer off a highway and crash, killing the driver and a man training to become a Catholic priest.

Investigators were looking into the possibility the driver had a medical issue that may have contributed to the crash Sunday that also injured 13 people, State Patrol Sgt. Blake White said. The coroner will make that determination about the driver, who has not been identified.

Jason Paul Marshall, a 53-year-old seminarian with the Albuquerque-based Archdiocese of Santa Fe, also was killed, the archdiocese said in a statement. He chaperoned the youth group that had attended a Catholic retreat in Denver.

The rest of the passengers, including young people and adults, were recovering from their injuries, the archdiocese said.

The group belonged to the Roman Catholic parish based at the University of New Mexico. Church officials in New Mexico and Colorado say the group had attended a retreat for 2,500 young people from 12 states in Denver and were returning home when the bus struck a bridge abutment and veered off Interstate 25 north of Pueblo.

At least one person was hospitalized in critical condition at Pueblo's Parkview Medical Center, nursing supervisor Kristina Wolf said. Others were being treated at hospitals in Pueblo and Colorado Springs.

Marshall, a native of Staten Island, New York, was a member of Our Lady of the Annunciation parish in Albuquerque and had attended the Pontifical College Josephinum in Columbus, Ohio, Archdiocese of Santa Fe said.

"Jason was a splendid and exemplary seminarian, a humble man who deeply cared for others," Archbishop John Wester said.

The Archdiocese of Santa Fe has scheduled a special mass Wednesday. The Denver archdiocese issued a statement Monday offering prayers and condolences to the victims, their families and their friends.

Three medical helicopters and dozens of ambulances and fire crews responded to the crash. There were extensive traffic backups in both directions as authorities extricated victims from the bus and treated the injured.