Four 1,000-litre containers of diesel sludge dumped by the roadside in Co Monaghan have been removed by council workers and the local fire brigade.

Two containers containing the toxic sludge were dumped overnight near the village of Annyalla and two in the townland of Drumleek in the Castleblayney area.

Both finds were in areas close to local watercourses.

Damien Treanor, acting Director of Environment with Monaghan Co Council, told RTÉ these latest dumping incidents bring to 54 the number of times the council has had to pick up and dispose of toxic diesel sludge this year.

To date in 2012 they have dealt with 290 tonnes of the sludge, which is a by-product of the illegal removal of dye from agricultural diesel.

The figures are substantially up compared with 2011, when the council dealt with a total of 37 dumping incidents, amounting to 198 tonnes of sludge.

Mr Treanor said it is costing Monaghan Co Council hundreds of thousands of euro to deal with the problem every year.