(CNN) -- A bus full of high school marching band members rolled on Interstate 15 in Idaho on Saturday night, killing an adult and injuring more than a dozen students, according to Idaho State Police.

The crash occurred about 7 p.m. MT just outside of McCammon, Idaho, police said. The bus was among a caravan of four carrying members of the American Fork High School marching band from Utah, said Capt. Eric Dayley. The students were on their way back to Utah, after participating in an invitational band competition at Idaho State University, he said.

The bus driver, who survived, had a medical condition that caused the crash, Dayley said.

The name of the adult killed was not released, according to Dayley. The victim was a chaperon, according to CNN affiliate KIFI in Idaho.

Two students were flown to Portneuf West Medical Center in Pocatello, Idaho, and at least a dozen others were taken by ambulance to the hospital, he added.

"Students from this crash have no life-threatening injuries," Dayley said.

About 50 students were on the bus when it crashed, police said.

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