Four men and two women were arrested today as part of a major investigation into money laundering linked to illegal dumping in Northern Ireland.
One of the men, aged 38, was held in Derbyshire where a diesel-laundering plant as well as machinery were seized.
Money was also recovered during 18 searches in Belfast, north Antrim and the Derrylin area of Co Fermanagh, where three men and two women were detained.
At one stage scientists from Queen's University in Belfast using equipment designed to locate deeply buried waste were called in to carry out to inspect one site.
The arrests follow lengthy intelligence-led operation against criminals making millions from illegal dumping on both sides of the Border.
A total of 150 officers took part, as well as police in Derbyshire and the Republic.
The Department of Environment in Northern Ireland has set up a special team to deal with growing levels of illegal dumping after it emerged that up to two illegal sites were being discovered each week containing tens of thousands of tonnes of waste from homes and businesses across the Republic.
Last September three truckloads of waste were seized in a joint cross-Border police operation.
Two months later an estimated £200,000 worth of stolen goods were found at a quarry near Derrylin, including tractors, one of which was traced back to Perth, Scotland.
Police believe criminals are involved in the theft and transfer of plant machinery worth £1.7 million every year.