Firefighters have extinguished a small fire inside the Australian Institute of Sport Arena in Bruce.
ACT Fire & Rescue arrived to find smoke coming from the arena's roof shortly after 8am Tuesday.
The Emergency Services Agency said firefighters discovered a small fire inside a transformer connected to lighting in the arena's roof and quickly extinguished it.
Damage was contained to the immediate area and firefighters had started ventilating smoke from inside the arena as of 8.20am.
Three fire pumpers, the HAZMAT unit and a commander were at the scene.
AIS staff alerted ACT Fire & Rescue to the fire.