Firefighters have battled fires in Ellenbrook and Bullsbrook overnight, with fears they may have been deliberately lit.
The Great Northern Highway in Bullsbrook has been closed from Warbrook Road to Warren Road as firefighters battle a blaze that started earlier this morning.
The Bullsbrook District High School remains open, the Education Department says.
Some school buses have been delayed because of road closures, but students who have arrived at school are being supervised as normal.
The cause of the Bullsbrook fire, which was reported at 2.40am, is not known.
This morning, a Department of Fire and Emergency Services spokesman said it could have been started by a flare-up from last week's fire but police are now investigating whether it was deliberately lit.
DFES are concerned that the Ellenbrook fire could also have been deliberately lit.
A DFES spokesman said there was "a bit of an issue" after another suspicious fire.
The fire started about 10.45pm near Zanzibar Loop in Aveley and was believed to be deliberately lit.
It took 30 firefighters nearly four hours to extinguish the blaze, which burned through two hectares of bushland.
Early yesterday, three suspicious fires in Brigadoon burned through about eight hectares and brought freight trains to a halt.
The previous night, about half a dozen spot fires in the Ellenbrook area kept firefighters busy from just after 8pm until midnight.
A bushfire advice has been issued for the Bullsbrook fire for people west of Walyunga National Park and east of Great Northern Highway from Warren Road to Warbrook Road in Bullsbrook in the City of Swan.
Motorists should avoid the area and be aware of fire and other emergency services personnel working on site.Sixty career Fire and Rescue Service, Bush Fire Service and Department of Environment and Conservation firefighters are on the scene constructing containment lines.
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