Firefighters worked through the night to control several separate blazes across the Perth metropolitan area.
A fire in Embleton caused $500,000 damage to a McKenzie Way home in the early hours of this morning.
One person was in the home when the fire, believed to be caused by a faulty water cooler, started about 12.30am.
It took firefighters half an hour to bring the blaze under control.
Bushfires were also reported in South Lake, Chidlow, Darlington and Upper Swan.
A Department of Fire and Emergency Services spokesman said two of the fires were accidental while the others are believed to be arson.
"Pretty much all of them happened at 9.30pm, so all at the same time," he said. "We were pretty busy all night."
The fire in Chidlow is believed to have started after residents did burnouts on their property while the blaze in Upper Swan started after a hot exhaust pipe made contact with grass.
Police are questioning people over the South Lake and Darlington fires, which are believed to be deliberately lit.