Lambton OPP say a body was recovered from the St. Clair River, south of Sarnia near Stag Island, over the noon hour Wednesday.
Constable Chris Doupe says they were notified around 12:45pm.
He says investigation revealed that passengers on a cruise aboard Sarnia's Duc d'Orleans spotted the body floating in the river and authorities were called.
Police responded and were assisted by the Canadian Coast Guard, the Point Edward Fire Department and Shell Refinery Marine Services.
Further information, including the name and gender of the deceased, has not yet been released.
Constable Doupe says a joint investigation with the Sarnia Police Service is underway because the city force is still investigating a missing person. 69-year-old Edward Alway was reported missing in April.
-With files from Josh Boyce
