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.
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.
Coolbellup Concerned Residents spokesperson Alison Wright said the group had 43 samples tested by the environment laboratory Envirolabs, which found more than 80 per cent contained asbestos.
She said dust clouds from the clearing and mulching work on the site were blowing through houses in the area.
"Because of the strong community concern a survey of the area proposed for the Roe 8 development, including some of the area that has since been cleared was conducted," she said.
"Asbestos like product is evident in large numbers throughout the project site and yet the Construction Management Plan only identifies specific areas to be addressed.
"This raises significant concerns about the ability of the contractor to properly mitigate against the risk of exposure to the public of dangerous levels of asbestos exposure."
Ms Wright said the asbestos posed a serious risk to locals' health.
"These samples were located throughout the area and found on the surface, buried in the ground either singularly or in large quantities," she said.
"Work should cease immediately until an adequate plan can demonstrate that residents and community are not at risk."
Last week, the City of Cockburn called on the Barnett government to halt work on Roe 8 because of fears the site was covered with asbestos.
Cockburn mayor Logan Howlett said the Environment Protection Authority and the Department of Environment Regulation should enforce "pollution provisions" to prevent dust impacting on nearby homes.
"The soil in these uncleared bush areas is extremely fine and prone to lift off," Mr Howlett said.
"These works should not be carried out until the autumn/winter when winds are seasonally lower velocity and the soil is more likely to be wet with rain.
"The city is also extremely concerned about reports of the presence of dumped asbestos material in the vegetation that is to be mulched and also in the bush that is to be cleared.
"There is a likely risk of asbestos fibres being released if asbestos is mulched or broken up."
Main Roads has been contacted for comment.