Twenty building sites in Co Wicklow and Dublin were supplied with material contaminated with a cancer-causing mineral from a local quarry.
The sites that received asbestos-containing material from the Co Wicklow quarry include a school under construction in Greystones and a variety of other building projects in the two counties.
The Irish Times revealed last week that Ballinclare quarry in south Wicklow has been closed, after testing last month uncovered the presence of naturally occurring asbestos in the stone it produces.
The problem arose when Kilsaran Group, which owns the quarry, blasted open a new seam of rock in one corner of the site.
Further inquiries have established that 20 sites in the two counties are affected by the dissemination of the contaminated building material from the quarry.
Eleven of these are to be remediated through the removal of contaminated material from nine sites in Co Wicklow and two in Co Dublin.
Some 25,000 tons of material will be returned to the quarry and covered with concrete and soil in order to render it safe, according to Wicklow County Council.