Update, 5.30pm: A fire which posed a potential threat to homes in Bullsbrook has been brought under control.
The Department of Fire and Emergency Services has downgraded the fire alert for the area from 'watch and act' to 'advice'.
The warning applies to people in Gibbard Place, Clarkson Road and Taylor Road in the eastern part of the suburb.
The fire started between Gibbard Place and Clarkson Road and was reported at about 2.34pm.
DFES says there is no threat to lives or homes but there is a lot of smoke in the area.
People in the area are being urged to stay vigilant and up to date.
Two helitacs, a type 1 helicopter and an air intelligence helicopter were sent to help fire crews on the ground.
It is not yet known what caused the fire which has burnt four hectares.
Motorists are also being urged to avoid the area.