The Fire Service was called to the small vegetation fire at the unoccupied Arthur St property at 5.30pm on Saturday.
Detective Sergeant Dave Nelson said the matter was passed on to police.
‘‘It's unexplained at this stage. There's nothing normal which could have caused it.
‘‘If anyone has any information which could help, we would like to hear from them.''
The fire appeared to have started in vegetation at the side of the house and burned some weatherboards, Det Sgt Nelson said.
The property was unoccupied and had been on the market for some time, he said.
Fire Service shift manager Andrew Norris said a Roslyn fire crew attended the fire.
● A St Kilda crew was called to a shed fire at a property on the corner of Council and Moreau Sts yesterday afternoon.
Mr Norris said the cause of the 3m by 9m fire was not known but it was not thought to be suspicious.
The owners of the property were not home at the time of the fire, he said.
