More than 50 building sites across the nation are suspected of illegal asbestos contamination from China, in a problem described as the "tip of the iceberg".

Asbestos Safety and Eradication Agency CEO Peter Tighe said he was aware of 64 sites where asbestos-tainted concrete fibre sheeting has been used in construction.

State workplace safety authorities are monitoring 17 sites in New South Wales, 13 in Queensland, 11 in South Australia and eight in Victoria.

Key points: So-called "asbestos free" building materials that actually contain the deadly compound continue to slip into Australia from overseas, despite an import ban

So-called "asbestos free" building materials that actually contain the deadly compound continue to slip into Australia from overseas, despite an import ban Workplace safety authorities are monitoring 64 building sites across the nation for asbestos, including 17 in New South Wales, 13 in Queensland and 11 in South Australia

Workplace safety authorities are monitoring 64 building sites across the nation for asbestos, including 17 in New South Wales, 13 in Queensland and 11 in South Australia Unions and victims are concerned the problem could worsen under the China-Australia Free Trade Agreement (ChAFTA)

"It's an emerging problem and it seems to be growing exponentially, as more and more products are brought into Australia, because of the wind-down of manufacturing in this country," he said.

"What we've really got now is really an indication which could be the tip of the iceberg."

Importing asbestos into Australia has been banned for more than a decade.

But the deadly substance is slipping into the country illegally from places like China, in products often certified as "asbestos free".

The popular building product, concrete fibre sheeting, is one area of concern.

Adelaide contractor RJE used the material, which was imported from China, in the flooring of two electrical substations in South Australia.

Recent tests confirmed the materials contained white asbestos.

Mr Tighe is worried about workers being unwittingly exposed to the new wave of asbestos.

"Our young tradespeople haven't been trained to deal with these products. They think they're asbestos free," he said.

"It's really a risk to these individuals, to their clients and to members of the public who might be in the vicinity when there's cutting, drilling or manipulation of asbestos cement products."

Adelaide contractor RJE used asbestos-containing material imported from China in the flooring of two electrical substations along SA's Seaford railway line. ( ABC News: Angelique Donnellan )

Jail terms for importers: Xenophon

Simon Pisoni from the Communications, Electrical and Plumbing Union is angry asbestos imports remain a problem more than a decade after the ban.

"We've seen the devastation that it's caused to people working on this type of material, and so for it to be imported and get that same exposure again is unforgivable," he said.

Workplace safety authority Safework SA said it was working with RJE on a plan to remove the asbestos in South Australia, but the product poses no health risk in the meantime.

RJE has previously said it believed the risk to workers who installed the sheeting in the Adelaide substations was "negligible".

It said it was assured the product was "asbestos free" when it was purchased from China.

Independent Senator Nick Xenophon is calling for more scrutiny of overseas building products and greater penalties.

"This needs a comprehensive approach [which] needs to include Customs doing their job, not just having random searches," he said.

"It needs certification of the supply chain so that if you're an importer and your product has asbestos in it, unless you've done everything possible to check and double check, you should face a potential jail term."

Sorry, this video has expired Asbestos victim Terry Miller tells his story ( Angelique Donnellan )

Products, importers and manufacturers on watch-list

Building products are not the only imports tainted with asbestos - children's crayons and car parts have also come under Australian Border Force (ABF) scrutiny.

The ABF said all cargo identified as "high risk" is physically examined, and the agency currently has a watch-list of more than 40 products, importers and manufacturers.

An ABF spokesman said the issue was discussed during a trip to China last year:

"The Commissioner met with a number of senior Chinese customs officials and discussed a number of border control and trade issues of mutual interest and concern. "The ABF continues to engage with relevant Chinese agencies to enhance cooperation on border issues of shared concern, including the importation of asbestos."

But the agency would not confirm which companies were currently under investigation for illegal asbestos importation in building products.

Unions have said the problem could worsen as a result of the China-Australia Free Trade Agreement (ChAFTA), a prospect that also concerns asbestosis victim Terry Miller.

Mr Miller worked at a James Hardie plant in Adelaide for 21 years, and is now president of the Asbestos Victims Association SA.

He is worried about a new wave of asbestos, and a new generation of victims, warning Australia could end up as a "waste dump".

"Customs just don't have the resources, don't have the manpower to inspect everything that's coming in," he said.

"What I would like to see is any company that's caught sending stuff here, or people who are getting it on the cheap because they can, if it's found to contain asbestos ... it should be sent back.

"There should be a significant fine and the company that produced it and branded it, as many of them do, "asbestos free" - if it contains that then I think that company and all its subsidiaries should be banned from sending anything into Australia."

Fines of up to $170,000 can be applied for illegal imports.

A Senate inquiry into non-conforming building products resumes tomorrow.