Officials are unsure exactly what caused the fire, which happened in a small structure behind the home at 301 W. Main St.
Watertown Fire captain Joe Fischer said the home owner had finished mowing his yard when he put the mower into the garage, which caught fire. The fire damaged two vehicles and the garage.
Officials had the fire is under control with WEMA and Watertown Fire responders on the scene just before 1 p.m.
Check back soon for more information.