Lexington firefighters extinguished a fire at 209 Londonderry Drive, in the Cardinal Valley area, on Thursday night.
Firefighters were dispatched at 7:12 p.m., and the back of the house was fully engulfed in flames when crews arrived. The fire was knocked down by about 7:40.
The home's owners were not injured, but a cat died in the fire. Firefighters and the homeowners were looking for a second cat, Maj. Maria Roberts said.
Investigators were working inside the home to determine how the blaze started, Roberts said.