Local authorities in the Leinster region are investigating reports that potentially defective building blocks allegedly containing pyrite have been supplied to a number of building sites.

In a statement in response to queries from RTÉ's This Week, the Department of the Environment said a potential problem was signalled to it in April.

It said the relevant local authority, which it did not name, "took immediate and appropriate action" to identify "if there was a problem and thereafter to determine the nature and extent of that problem".

The statement said the supplier of the allegedly defective blocks had been co-operating with the investigation, which is ongoing.

Pyrite expands on contact with water or where there is moisture in the air.

The Royal Institute of the Architects in Ireland (RIAI) and the Association of Consulting Engineers both notified their members in May of instances of apparent pyrite content in concrete blocks provided by unnamed manufacturers.

The RIAI's warning to its members states: "The problem, as identified, where concrete blocks containing pyrite are used structurally, is likely that the structural integrity of the block-work will need to be investigated, in particular where it is in contact with moisture/water."

Separately the Department of Education has issued a statement to RTÉ News regarding a query related to a school that is under construction in north Dublin.

The department said: "The contractor has forwarded materials for testing to an independent laboratory.

"The Department is awaiting a detailed report from the contractor on the matter.

"On receipt of the contractor's report the Department and its Design Team will then determine what next steps are required," it said.