The North Bay OPP is investigating the drowning of two people in Legrou Lake, south of Arnstein, in East Mills Township.
Emergency crews were dispatched to a capsized canoe just before 7:30 pm Tuesday.
The OPP says four people were in the canoe with two able to swim to shore.
Police report a third person was located by neighbouring cottagers and life-saving techniques were attempted but the person was pronounced deceased.
The OPP Underwater Search and Recovery Unit will be attending to assist in locating the fourth person.
Police say the investigation is ongoing under the direction of the Office of the Chief Coroner for Ontario and the Ontario Forensic Pathology Service. No names are being released until the next of kin have been notified.