A family, including children, were prohibited from returning to the house, in Canberra's south, after inspectors from WorkSafe ACT visited on Tuesday.

Work Safety Commissioner Mark McCabe also put a prohibition notice on further work on the house, which was being renovated, and asked his major investigations unit to look into any breaches of the law.

Testing had found amosite asbestos, the most deadly form of the building material, on a range of surfaces through the house, and on materials in a trailer outside, he said.

Inspectors determined that the work was not being done safely, the builder may have been unlicensed, and no development approval documents had been found.

The home owners and the builder knew it was a Mr Fluffy house.

''This is the first case I have seen where there has been such a flagrant issue arise in what was known to be a Mr Fluffy house,'' Mr McCabe said. ''What has happened in this case, it's hard to understand, given the publicity there has been about this issue.''

There was a high chance the builder and his workers had been exposed.

''I understand the family is very concerned … and the tragic thing about these kinds of situations is you may not know for a long time whether you actually incur any medical consequences, so you can live with that sitting over your head.''

Inspectors immediately told neighbours, but Mr McCabe said air tests had not detected asbestos fibres above background levels.

''Because air monitoring has not shown the presence of any fibres, there's no current risk to the public and the material outside has been sealed. As to whether there was exposure prior to our intervention, we can't ascertain that,'' he said.

Anyone who is concerned should see their GP.

Mr McCabe would not give the house's address, beyond confirming it was in Pearce. It was one of the 1049 homes identified as having the loose ''Mr Fluffy'' asbestos installed in the ceiling as insulation in the 1970s and removed during a clean-up program between 1988 and 1993.

The householders were also part of the mailout in February this year warning people in Mr Fluffy houses that some of the insulation might remain in wall cavities and other spaces, such as under the floor. Home owners were warned against any renovation or disturbance of walls, subfloors or eaves without an asbestos inspection.

Mr McCabe is still trying to establish when renovation work began at the house in Pearce, but said wall panels had been removed inside, along with parts of the exterior wall.

WorkSafe was getting advice on how to remediate the house, and Mr McCabe said the family could be out for some time.