The Terre Du Lac Fire Department responded to a house fire a little after midnight on Friday at 1216 Estates Lane.
Chief Anthony Groves said fire escaped from the fireplace and the residents woke up to smoke alarms and heavy flames in the back of the house.
There was extensive damage to the upper floor, Groves said, estimating about 60% of it being destroyed.
The only injuries reported was a minor injury to a firefighter that was not fire-related, he said.
Big River/Bonne Terre, Park Hills, Potosi, Irondale, Farmington, Leadington, and Bismarck fire departments assisted Terre Du Lac.