Workers may have come into contact with asbestos despite warnings from the long-term resident property manager Ben Broers that the area they were working in was contaminated. Mr Broers has subsequently had his contract terminated by ACT Health and has been asked to sign a confidentiality agreement.

The directorate started building works two months ago at Miowera, a property in the Tidbinbilla Valley. The government bought the land in 2008 to build an indigenous drug and alcohol rehabilitation service – to "reconnect Aboriginal and Torres Strait Islander peoples to land and culture, using participation in land management activities and programs".

The 320-hectare site has extensive asbestos contamination due to remnants of two bonded asbestos sheet houses that burnt down in the 2003 fires, the asbestos sheeting from the Old Cotter Pub, and other asbestos refuse from around the region which has been dumped in a landfill gully. Hundreds of metres of asbestos fencing have also been bulldozed over the years, leaving asbestos footings submerged in the soil.

The site has been mired in controversy since the government purchased the land almost seven years ago for $1.5 million - fighting repeated planning objections by neighbouring landowners to the proposed $11 million eight-bed facility. Planning Minister Mick Gentleman used his call-in powers to override those objections in October with work beginning in November.

On November 19, however, contractors unearthed and broke old asbestos piping while strengthening a bridge over Paddys River to access the site.

Work Safety Commissioner Mark McCabe said he was satisfied that the risk had been managed when workers covered the pipe with soil and wet it down. Mr McCabe said the risk to the water supply was "extremely low".

Mr Broers, meanwhile, sought to warn ACT Health directly that the site in which workers continued to dig and sandbag contained contaminated soil.

He rang ACT Health on November 28 to explain the risks and, when work continued, further texted his manager on December 1. But it was not until the directorate received a Robson Environmental report on December 2 that work was stopped.

A spokesman for Health Minister Simon Corbell said: "On receiving the advice on December 2 that asbestos-containing material was present around the bridge worksite, ACT Health spoke to the subcontractor and it was decided to halt the work until the plan was updated and a safe method work statement developed".

Mr Broers, who has managed the property for eight years, was informed on January 5 his contract had been terminated. Mr Corbell's spokesman categorically denied it was a result of the asbestos incident and that the contract was due to expire in March.

Mr Broers said he believed his outspokenness to bureaucrats over workers spending four days on a contaminated worksite had resulted in his contract not being rolled over as it had each year.

Mr McCabe said Worksafe was now monitoring the site closely. He said ACT Health had not made the inspectorate aware of the full extent of on-site contamination. Robson Environmental has placed 30 red flags indicating asbestos sheeting fragments near the farm buildings.

Following inquiries from The Canberra Times on Thursday, Mr McCabe requested information from the directorate about "all aspects of the asbestos contamination at the site including plans for its removal and the remediation of land".

Meanwhile, ACT Health has downplayed the risk to a general contractor Robbie Wallace who was hired on November 19 to mow tree lanes at the property - an area subsequently confirmed to contain further broken asbestos sheeting, which was hidden by long grass.

Mr McCabe said no mowing should have occurred in the area and he was still investigating the issue.

Bonded asbestos sheeting is considered safe until broken into pieces, when asbestos fibres can become airborne. Mr Wallace is receiving legal advice.

Neighbouring property owner Michael Shanahan, upon whose land the broken pipe is located, said the government takeover of the property had been rushed through and questioned whether planning and safety processes had been fully adhered to.

Mr Corbell's spokesman said, "ACT Health is confident that they have followed appropriate processes and procedures and believe that the risk of any residents or workers having been exposed to asbestos fibres is extremely low".

Mr Shanahan is one of the complainants who objected to the drug and alcohol centre being built. Similarly, neighbours David and Margaret Whittem objected and feel their concerns about safety and management of the site had been ignored.

Mrs Whittem questioned why she had received no formal warning that asbestos had been disturbed on the river upstream from her property - condemning both the directorate and WorkSafe's handling of the issue.

Mr Shanahan believed Mr Broers had been a scapegoat after calling the directorate to account on the issue.

"I do believe he is paying the ultimate price when all he has tried to do was warn of the risk to neighbours and workers on the site."