South Simcoe Police say the province's Special Investigations Unit (SIU) has invoked its mandate following a "serious incident" in Innisfil.
"As a result, the South Simcoe Police Service is unable to comment," police added in a tweet on Tuesday night.
Barrie Police confirm they are assisting South Simcoe Police with the incident.
Numerous reports indicated a heavy police presence in the area of the 25th Side Road and 9th Line, with reports of a police-involved shooting.
"Please await a formal statement from our Corporate Communications Officer and Acting Chief Van Dyke and in the interim please pray for all those involved," retired South Simcoe Police Chief Andrew Fletcher tweeted late Tuesday night.
The SIU is an independent government agency that investigates incidents involving police officers that may have resulted in death, serious injury, sexual assault, and the discharge of a firearm.
