The Fire Marshal is working to determine what sparked a fire at an apartment complex in Norwalk on Sunday.
Firefighters were called to an apartment on Soundview Avenue after getting a report of a structure fire.
When crews arrived, they said they found the third floor apartment well involved with fire.
Two hose lines were stretched to the apartment to help extinguish the flames, firefighters said.
Multiple rooms in the apartment had extensive fire damage and two others were damaged by heat and smoke. The apartments on the first and second floors also sustained water damage, according to fire officials.
Firefighters said the building has been deemed unfit for occupancy and the cause of the fire is under investigation.
No injuries were reported.