Monaghan County Council environment officers launched a major clean-up operation yesterday morning after the discovery of 10 to 12 tonnes of chemical waste by-products from illegal diesel laundering operations along the Border.
The find was made on a roadside at Mullyash, Castleblayney, near the south Armagh border.
The county's senior environmental officer, Mr Gerry Kelly, condemned the people who dumped the sludge on a roadside.
It would cost Monaghan County Council up to €4,000 a tonne to dispose of the waste safely, he said. Mr Kelly warned that when the people responsible are caught they will face the full rigours of the law.