Two young men and a woman are in police custody after heavily armed officers raided a Cabbagetown high school Tuesday over reports of a person with a gun.

Officers at 51 Division and the Toronto Police canine and emergency task force units rushed to Parliament and Winchester Sts. just after 9 a.m. responding to a 911 for a robbery, said police spokesperson Caroline de Kloet.

Police then entered Monseigneur Fraser College’s St. Martin campus, an alternative and adult Catholic secondary school.

The school administration placed the building under lockdown as police arrested two men under 18 years-old. A woman, whose age is unconfirmed, was also arrested nearby.

The lockdown has since been lifted, and the investigation is ongoing.