Service has resumed at a downtown Toronto subway station after police were called in for an investigation related to a person with a gun.

Officers were called to Ossington Station on Line 1 at around 12:40 p.m. for a security incident.

According to investigators, bullet casings were found on the bus platform outside the station. As of Monday afternoon, police have not reported any injuries.

No further details have been provided regarding the potential firearm incident, however police say they are searching for a suspect who fled westbound on foot before possible leaving in a vehicle.

Subway trains and busses bypassed the station for a few hours while police investigated.