A Hamilton high school was placed on lockdown after a report of a potential threat on Monday afternoon.
Const. Jerome Stewart said Hamilton police received a call at 12:33 p.m. about an incident at Westmount Secondary School and that a lockdown was put in place.
Police said they received information that a student at the school had a firearm.
During the lockdown, officers detained three male students and recovered a pellet gun.
The lockdown was lifted shortly after 1 p.m.