Fire communications shift manager Riwai Grace said Fire Service crews from City, St Kilda and Lookout Point attended a house fire in Moreau St, St Kilda, at 4.30pm.
Detective Jenepher Glover, of Dunedin, said the house was being renovated and nobody was inside during the fire.
The fire had started in the kitchen, which was ''extensively damaged''. The adjoining laundry and toilet had smoke and heat damage, she said.
''We don't know what started the fire, but it is being treated as suspicious.''