It is the second time costs have blown out in the demolition due to asbestos, with the cost originally put at $3 million. In August 2015 it was revealed that the cost had escalated from $3 million to $6 million, as a result of extensive asbestos finds.

The government signed a contract with Manteena in June last year for $6.25 million. In August this year, the contract was varied to add another $7.34 million, to a total $13.59 million. The blow out is revealed in the Land Development Agency's annual report.

Agency chief executive David Dawes said the final cost was expected to be about $14 million. He attributed the cost blow-out to significant areas of asbestos found embedded in the concrete walls. As a result, all rubble had to be treated and disposed of as asbestos-containing material, he said.

Demolition is almost complete at the landmark city site, on the corner of Ainslie Avenue and Currong St, near Gorman House.

The site was bought by developer SHL in February this year for $47 million. SHL, owned by Jia Liang, is also the developer of Campbell 5. It is responsible for demolishing the Allawah public housing flats in front of the Currong flats, and will convert the entire site to 515 new apartments, in buildings from three to 12 storeys, and commercial space.

The Currong public housing contained 212 units and was rented more recently to university students. Built in 1959, they were six L-shaped blocks, each eight stories. There are 114 units in the Allawah block.

A 2015 report from Robson's found extensive asbestos at Currong. Friable asbestos was used as spray insulation on pipes in utility cupboards and boiler rooms. Insulation packing around cables through the floor and ceiling slab contained asbestos and asbestos sheets lined kitchen units. Vinyl floor tiles, woven sheath on electrical cables and window and door putty also contained asbestos.

That report resulted in the change from demolition costs of $3 million to $6 million.