Appleby College in Oakville has been placed in a hold and secure following a report of gunfire in the area, according to police.
Staff and students are advised to remain inside their facilities until further notice.
Police say Lakeshore Rd W is closed from 4th Line to Birch Hill Lane for the investigation. Residents are advised to avoid the area.
Halton police are asking all residents in the area to immediately shelter in their basements until further notice.
This is an active situation, according to police.
There is a heavy police presence in this area, including frontline officers, the Tactical Rescue Unit and K9.
Police say the initial call was received shortly before 1:20 pm reporting possible gunfire in the area.