Firefighters said they were called to the complex on Discovery Street about 9.20am, and sent four fire trucks to the scene.

"Quick work by fire crews prevented the blaze from spreading to adjoining units," the agency said in a statement.

"The unit complex was evacuated as a precaution."

Police said the fire caused extensive damage to the unit, and one other adjoining unit was also affected.

"Following an analysis of the scene, police and fire investigators believe the fire was deliberately lit and deemed it suspicious," police said.