CHEHALIS, Wash. -

The Washington State Patrol says a school bus driver and five middle school students needed medical attention after a 13-year-old discharged pepper spray inside a packed school bus en route to a Mount St. Helens field trip.

Troopers say 46 students were headed south from Tumwater on Monday morning when the spray filled the bus. KOMO-TV reports that the 28-year-old female bus driver stopped on the shoulder of Interstate 5 when she began having breathing problems. Medics and troopers treated five students directly exposed to the spray. Troopers say the driver was the only person who went to a hospital for additional treatment.

The State Patrol says the student who discharged the spray handed the container to another student, who passed it off to a third student. All three were taken back to school officials. The district sent another driver and the field trip continued.