Gardaí and customs officials have raided an illegal oil-laundering plant near Carrickmacross in Co Monaghan.
Up to 10,000 litres of washed diesel and a mobile laundering facility were seized during the raid in the Carricklane area.
Customs officers said the plant was being used to wash the dye out of red diesel, which is sold cheaply to farmers in the North.
The washed diesel would then be sold on to motorists for an inflated price.