Monaghan County Council is investigating the illegal dumping of old tyres, following the discovery of hundreds in a country lane at the weekend.
An estimated 20 tonnes of tyres were found dumped near Castleblayney, Co Monaghan.
In the previous week officials from the council stopped and impounded a lorry carrying a load of tyres.
The lorry was not authorised to carry waste, and it is believed the plan was to dump the tyres at an illegal site along the Border.
Yesterday a spokesman for Monaghan County Council said officials were working closely with gardaí in both cases, and had linked the recent discoveries to the rising cost of disposing of disused tyres. Tyres cannot be landfilled, and are highly toxic if burned.
They are easily recycled into rubber crumb, a product that is used in everything from building materials to playground safety pads.
Some tyre firms have been charging a €2 "environmental levy" a tyre to take them away from garages. The garages have been passing the cost on to consumers.
Last month the Minister for the Environment, Mr Roche, said he had instructed his Department to write to the Irish tyre industry representatives over this practice. He pointed out that there was no provision in any legislation for this levy.
Last month the only tyre recycling company in Ireland, Dundalk-based Rubber Crumb Ltd, said it was having difficulties getting enough tyres to keep the company running efficiently.