Fifty people were evacuated from London Circuit's Metropolitan Apartments following an automatic fire alarm on Friday night.

A resident also phoned emergency 000 to report the smell of smoke.

An Emergency Services Agency spokeswoman said four ACT Fire and Rescue pumpers, the Bronto Aerial Unit and a commander were on the scene as of 9.10pm.

Crews searched the 12-storey building for signs of fire and found substantial smoke on the 11th floor caused by an electrical short in a light fitting.

Residents were allowed back into the building after atmospheric testing.