Melbourne's asbestos contamination widens to four sites as the EPA comes under fire

An asbestos contamination in Melbourne's west has widened to four parks as the state's Environmental Protection Authority is accused of contradicting itself.

Three more sites have tested positive to asbestos in Altona North, hours after the EPA declared asbestos-contaminated mulch discovered at a playground in Spotswood on Thursday was an "isolated" find.

Since Victoria's first asbestos discovery this week, neither Hobsons Bay Council nor the EPA have agreed to an on-camera interview.

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Williamstown MP Melissa Horne, however, said both parties are busy proactively working together to identify asbestos and investigate.

"The crucial concern remains. How many more parks could be contaminated with asbestos," she said.

"And the big question the community wants answered is: 'Where has this dodgy mulch come from?'"

Horne could not answer how many suppliers supply to different councils.

Local mum Alison Gibbons said the asbestos discovery was worrying and condemned the local council for its use of dangerous materials.

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"For her health and my health, my babies, it's very worrying," she told 9News.

"They need to be using better quality materials."

Meanwhile, experts have warned that the industry is largely unregulated.

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"Everyone's trying to save a dollar and wherever they can buy materials for a reduced rate and put it into their project. They'll be doing it," managing director of GMA Group Steve Marett said.

"Anyone can buy an excavator and start processing this material and selling it as second hand recycled mulch."

Asbestos has also been found in multiple parks in Sydney.