Residents' fears the plumes of dust from the Roe 8 clearing in bushland in Coolbellup were covered with potentially deadly asbestos have been confirmed, after testing found the toxic material on the site.

The Barnett government is currently clearing bushland along the route for the contentious Roe highway extension, which is part of the Perth Freight Link.

A document outlining the testing which was done.

Residents had known for years part of the area has been a dumping ground for asbestos and raised concerns to the WA government the dangerous material was getting mulched and blown into nearby homes.

Main Road workers, covered in protective gear, had been on the site recently removing illegally-dumped asbestos.