Investigations are under way after it was discovered that a State agency has been dumping at an unlicensed landfill site.
The Department of the Environment admitted yesterday that the "unauthorised" dumping took place.
The material includes large amounts of commercial waste.
Dúchas, the national heritage service, has already started an internal investigation into how a truck from the Dúchas depot in Kilkenny city went to a site outside the village of Killenaule in South Tipperary and deposited material there.
Tipperary Co Council (South Riding) and the Southern Regional Fisheries Board are also investigating.
The Department of the Environment issued a statement yesterday, which said: "The Department regrets that unauthorised disposal of waste appears to have occurred from its Kilkenny depot.
"The matter has just come to light and is being fully investigated.
"The disposal will immediately cease and the Department will comply fully with the environmental regulatory authorities in relation to the matter."
It is understood the Department, which took over responsibility for functions of Dúchas in June of last year, is currently overhauling its areas of responsibility with a view to improving their management. The Government decided in April to break up Dúchas.
The site is on a game reserve in a scenic area, near the village of Killenaule, Co Tipperary, at Burnchurch, Moyglass. The driver of the lorry was recently seen setting two fires on the site before he left the illegal dump.
The material left there included two storage heaters, lagging, plastic bags, a number of large bags of concentrated lime, chairs, rubber, paper, cardboard and Dúchas brochures.
It included refuse, including milk cartons, plastic bottles, and portions of food waste, plastic piping, bags of cement, plastic buckets, large metal barrels, plastic covering for silage and copies of Heritage Week 2000.
The site backs on to a small fen or lake, which has been partly covered by the material.
A strong critic of Dúchas, Mr John McGuinness TD of Kilkenny, wants to know why the State agency with responsibility for the country's national monuments is using an unlicensed dump to place its refuse when there are legal dumps close to it which it can use.
"I believe that this is not a once-off. I know that material from other Dúchas sites in Clonmel and Cahir has also been deposited here," he said.
He said he wanted to know how much the landowner was paid by Dúchas and for how long the site had been used by them.
A spokesman for Tipperary South Riding Co Council, Mr Jimmy Harney, said the council was investigating.
He confirmed there was no permit for the site and that it was operating without planning permission.