The Police Service of Northern Ireland is assisting gardaí in tracking down those responsible for dumping thousands of litres of sulphuric acid in Co Monaghan close to the Border at south Armagh.
The chemical substance discovered this week is the "drain-off" from a fuel-doctoring operation by racketeers who remove tax-rebated colouring from diesel.
Once the colouring is removed, the diesel can be sold as commercial fuel, thus enabling the distributors to make huge financial gains.
Environment officials from Monaghan County Council were yesterday examining several barrels of the fuel which were dumped at Lannett Road, near Inniskeen.
Huge costs are being incurred by local authorities in recovering dumped chemicals safely in order to curtail damage to the environment.
Local authorities are also compelled to pay hauliers to take the sulphuric waste to ports for shipment to Germany, where it is incinerated.
Last night, Garda sources in Co Monaghan said they were "fairly certain" who was responsible for the illegal dumping.
"We are currently getting co-operation from the PSNI on this matter," a spokesman said.