Cudahy Fire told CBS 58 News smoking in bed likely set off a mattress fire that spread causing a house fire late Tuesday night.
Two men who lived at the home in the 3800 block of Armour Ave managed to escape without injury despite working smoke detectors in the house.
The fire was discovered just after 11 p.m. on Tuesday.
Cudahy firefighters arrived and quickly put the fire out but not before it damaged much of the second floor.
While the fire department issued a MABAS mutual aid box alarm the fire the scene was cleared within an hour.
Damage estimates were not released.