UPDATE 3pm: Detectives from Bendigo CIU are treating the fire as suspicious and have called for any witnesses to come forward.
Anyone who may have seen two young boys in the area beforehand is asked to contact Crime Stoppers on 1800 333 000 or submit a confidential report at www.crimestoppersvic.com.au
EARLIER: Police are investigating after a fire in a vacant house in Golden Square.
Firefighters were sent to the Olympic Parade property about 12.45pm after receiving multiple calls.
Kangaroo Flat Fire Brigade fourth lieutenant James O'Brien said the fire started in a bedroom of the vacant and derelict house, and it was partially alight when crews arrived.
He said thanks to a quick response by the CFA, crews were able to minimise the damage to about 15 per cent of the house.
Neighbour Darren Bradley said the house had been vacant for about eight years, with teenagers often using it for parties at night.
He said they were there nearly every weekend, but it was the first time something like this had happened.
Four appliances from Kangaroo Flat responded to the blaze, along with two from Bendigo.
Police were also called to Olympic Parade to direct traffic as firefighters worked at the scene.