Emergency services were called to King Edward Court in Dunedin as it filled with smoke yesterday morning.
Five fire engines were sent to the blaze and the westbound lane of Stuart St was blocked for a time.
A Fire and Emergency New Zealand spokesman said it was called to the scene, in Stuart St, at 8.33am.
"When the crews arrived, the building was filling with smoke."
Firefighters quickly established that an electrical light fitting, which had malfunctioned, caused the fire, he said.