Police are treating a fire that caused the evacuation of a Braddon apartment block as suspicious.

Three fire pumpers, breathing apparatus support and a commander arrived at the fire on Fawkner Street about 11.20am on Wednesday.

Residents were evacuated as ACT Fire & Rescue forced entry into the building.

Emergency services said the unit was "well-alight and heavily smoke-logged" however the damage was contained to the apartment.

Police ask that anyone who may have information about the fire to contact Crime Stoppers on 1800 333 000 or via the Crime Stoppers website. Please quote reference P1559957.