A mezzanine level between the ground and first floor has now collapsed which has made access to the remaining fire more difficult.
Fire has been extinguished on the ground floor of the premises.
This has allowed firefighters to enter the building to actively attack the remaining fire upstairs.
ACT Fire & Rescue was initially alerted to the incident by an Emergency Triple Zero (000) call.
Fire crews have contained the fire to a single tenancy within the commercial building where it started.
Firefighters continue working to extinguish the blaze from the ground and above.
Firefighters are working to extinguish a building fire in Fyshwick.
The alarm was raised at 3:16am. ACT Fire & Rescue responded to the incident in Tennant Street with four fire trucks, the Bronto aerial platform, breathing apparatus support van, HAZMAT unit and commander.
The two storey building is fully engulfed in fire.
The fire has now been fully extinguished.
Fire crews are damping down the affected area.
A bedroom has sustained fire, smoke and water damage while the remainder of the home has been heavily smoke damaged.
The initial estimated damage bill is in excess of $150,000.
Firefighters will shortly commence ventilating smoke from the property which will be followed by atmospheric monitoring by the HAZMAT crew.
The cause is unknown but will be investigated.