A weapon was discharged “multiple times” during an altercation between two Niagara police officers in Pelham, Ont., leading to one of the officers being critically injured, according to Ontario’s Special Investigations Unit (SIU).

The officers were in the area of Effingham Street and Roland Road, about 20 kilometres west of Niagara Falls, conducting an investigation into a collision that occurred a few days earlier when the weapon was discharged.

A 52-year-old police officer was transported to St. Catharines before being airlifted to Hamilton General in critical condition.

The SIU previously said that the shooting was a result of “an interaction between two Niagara Regional Police Service officers.”

“One officer discharged his firearm multiple times, and the other officer was struck,” SIU spokesperson Monica Hudon said in a news release issued Friday afternoon. “The officer who was struck was transported to hospital where he is in stable condition.”

The SIU has assigned eight investigators and three forensic investigators to this case. The victim of the shooting and 12 other officers have been designated as witnesses by the SIU.

One police officer has been designated the subject of the investigation.

No other information has been provided by the SIU or by Niagara police about what led to the altercation between the officers.

In a statement issued Thursday evening, Niagara Regional Police Chief Bryan MacCulloch said that no arrests had been made in connection with the incident.

“In the spirit of transparency, I have asked the Ontario Provincial Police to determine if there is any criminal culpability outside of the SIUs scope,” MacCulloch said. "The days and weeks ahead will be trying ones for the NRPS family and the community we serve. I ask for your support for our members and all those involved."

The SIU is asking anyone with information about the investigation to contact authorities at 1-800-787-8529.