Hunt on for arsonist after bushfire that blacked out Perth sky

Arson Squad detectives are hunting an arsonist who lit a bushfire in the Perth hills that burnt about 4,000 hectares of forest and created an eerie smoke screen over Perth yesterday.

The fire was lit around 8.30am yesterday near Gorrie Road near Chamber Road in Sawyer’s Valley.

Detectives from the Arson Squad’s Strike Force Vulcan are investigating at the ignition point today.

Officers would like to speak to the driver of a grey, early 2000s model Ford Falcon that was seen on Gorrie Road in the area of Hancock Brook.

9NEWS has gained access into the fire zone where bush land has been destroyed.

More than 150 fire crews worked through the night to contain the blaze.