A vacant miner's cottage in Addington Road, Creswick was destroyed by fire early this morning.
The fire happened at 4.55am and was eventually put out by crews from Ballarat City, Creswick and Clunes fire brigades.
Moorabool CIU investigators believe the fire to be suspicious, but have not released any further details.
The house was in an isolated part of Creswick, in a unnamed lane with only four houses. No other houses were damaged.
Police called on witnesses to come forward with information, by calling Moorabool CIU on 5366 4545 or CrimeStoppers on 1800 333 000.