There has been a significant rise in the number of incidents where sludge has been left on roadsides around the northeast.
Monaghan County Council had just one incident in 2010, but last year that rose to 37.
It is estimated the council has spent over €1.5m since 2004 removing the sludge that is usually left in containers.
Louth County Council says the amount of sludge found after illegal diesel laundering increased four-fold last year.
Just under 1,000 tonnes were recovered and cleaned up at a cost of almost €1m.
There were 90 incidents where sludge was found and removed, according to the council.
A total of 989 tonnes of material had to be taken and shipped to Germany for incineration at a cost of just under €1m.
This represents a huge rise on previous years. Back in 2009, just 72 tonnes of material was found, but that rose to 220 tonnes in 2010.
The sludge is usually left on roadsides in large containers known as IBCs, which hold around 1,000 litres each.
Often these containers are in poor condition, which results in the sludge leaking and contaminating the ground.
The sludge is created after the green dye is removed or washed from agricultural diesel and then sold on as more expensive road fuel.
The criminals and service stations selling the fuel profit on the difference.
There have been four more discoveries of diesel sludge dumped along country roads in Co Louth this afternoon.
It is possible the containers holding the toxic waste may have been dumped by the same gang, but the local authority believes it is more likely they were dumped by several gangs involved in laundering diesel.
