Gwinnett County fire investigators have determined that a house fire that broke out Wednesday in the 4200 block of Hillbriar Court in Buford was caused by an improperly discarded cigarette.

The cigarette caught the living room sofa on fire, but the blaze burned itself out before spreading. Two occupants were displaced because of soot and smoke damage throughout the house.

Gwinnett fire Capt. Tommy Rutledge said careless smoking is the leading cause of home fires. A cigarette butt dropped on a couch cushion can smoulder for hours before bursting into flames.