A fire at a derelict house in Mandurah is believed to have been deliberately lit.
Firefighters were called to the house on Stewart Street near Beam Road around 7am on Wednesday.
The house was engulfed in flames.
It took fire crews just over an hour to extinguish the blaze.
The cause is believed to be suspicious.
It's understood the house is often used by squatters.
The Arson Squad are on their way to the scene.
Anyone with information should contact Crime Stoppers on 1800 333 000.