A student released pepper spray inside a classroom at Derby High School at about 12:30 p.m. Tuesday, firefighters said.
Derby High School employees called the fire department after about 30 students complained about not feeling well.
Symptoms included watery eyes and coughing, according to Derby Fire Department Chief William Nicoletti.
Firefighters brought in a hazmat team and tested the air inside the classroom. Eventually a firefighter saw a discarded pepper spray container in the trash, Nicoletti said.
The doors and the windows in the classroom were opened to vent the room.
Officials then called in the Derby Police Department. Officials said the student responsible for the incident was taken to the principal’s office.
Derby police were investigating as of 1:15 p.m.
Nicoletti said students went to the nurse’s office to get checked out.
“Our EMS people told the nurse and the principal that if anyone has any symptoms just to flush their eyes and wash their hands. Anything more than that should be treated at a hospital,” Nicoletti said.