Three bullets have been found in an upstate New York high school where students were confined to classrooms in a lockdown that lasted more than four hours.

Rome Superintendent of Schools Jeffrey Simons says the lockdown at Rome Free Academy began at about 10 a.m. Wednesday after a .22-caliber bullet was discovered by students in a technology classroom. A search by authorities of classrooms and nearly 3,000 lockers turned up two other bullets.

Rome Public Safety Commissioner James Masucci says having bullets in school isn’t a crime so no one will be charged, although the school may impose disciplinary measures. Simons says school authorities are still working to determine who brought the bullets to the school.

Students were released from their classrooms at 2:30 p.m.