St. Clair Township firefighters responded to a cottage fire on Fawn Island at around 10:45pm Sunday night.
Firefighters and portable pumps were transported to the island, south of Sombra, on the passenger ferry.
There was extensive damage to the structure and some damage to hydro infrastructure on the island.
No damage estimate is available yet, the investigation into the cause of the blaze is ongoing, and there were no injuries.