Arson squad detectives are investigating after four house fires in the past 24 hours.
A Bullsbrook home has been gutted by a suspicious fire this morning.
Firefighters were called to the Old West Road house just after 8am to discover the home fully involved in flames.
It took crews about 30 minutes to get the fire under control.
It is understood emergency services were called to the house last Sunday morning after the front area of the home was allegedly deliberately lit.
Last night, firefighters were also called to a house in Banyard Avenue in Kelmscott at about 7.45pm. Crews rescued an unconscious man from the burning building.
The fire was brought under control in under 50 minutes. About $300,000 damage was caused by the blaze.
At 8.45pm crews were called to a home on Cross Street in Queens Park.
Firefighters from Belmont, Kensington, Perth and Osborne Park tackled the blaze in about 40 minutes. The blaze caused about $250,000 damage.
About 9pm fire crews were called to a house on Hubbard Way in Medina. The Homeswest home sustained an estimated $100,000 damage.
All fires are being treated as suspicious until determined otherwise.
Anyone with information is asked to contact Crime Stoppers on 1800 333 000.