Police arson squad officers are investigating three suspicious house fires in and around Perth last night.
Between 9am and 11.15pm, a large group of youths held a party at an abandoned property on Thompson Road in Roleystone.
The revellers set fire to rubbish and furniture in the house, sparking a blaze which spread to the roof.
A Department of Fire and Emergency Services spokesman said the blaze caused about $100,000 worth of damage.
Just after 9pm in Mandurah, police and fire crews rushed to a house fire on Foulkes Place.
It is understood the roof of the property collapsed before firefighters brought the blaze under control by 9.50pm.
The damage was estimated at $150,000.
Finally, just after 3am, emergency authorities were called to a fire at an unoccupied house on Baron Way in Gosnells.
It is understood the house was all but destroyed, leaving a damage bill of about $300,000.
Arson squad officers will attend all three properties today to investigate.
Anyone with information is asked to call Crime Stoppers on 1800 333 000.
In an unrelated incident, a 19-year-old Greenfields man has been charged with deliberately lighting a bush fire in Warnbro yesterday.
Police will allege the teenager set fire to scrub next to Ennis Avenue just before 5pm.
A DFES spokesman said the grass fire covered about 6000sqm at its peak.
He has been charged with wilfully lighting a fire likely to injure or cause damage.
He is due to appear in the Perth Magistrates Court today.