Two held over illegal waste dumping in northern England and Midlands
Two men have been arrested after up to 25,000 tonnes of waste were dumped in sites across the North of England and Midlands.
Dawn raids were carried out at five addresses connected to addresses in Staffordshire, Herefordshire and Hertfordshire.
Waste has been dumped at 17 sites in the Midlands, North West and North East.
A third person is helping police with their inquiries.
The arrests were made for offences relating to Section 33(1)(a) of the Environmental Protection Act 1990, and Reg 38(1)(b) of the Environmental Permitting Regulations 2010.
The Environment Agency said the men have been released subject of further inquiries.
The EA said its investigation, codenamed Operation Cesium, had been running since last summer.
The dawn raids at the suspects' home and business addresses were supported by more than 20 police officers from Staffordshire, West Mercia, Warwickshire and Hertfordshire.
The arrests were made in the Herefordshire town of Ledbury and in Rickmansworth, Hertfordshire, the agency said.
The investigation is expected to continue for months.
Paul Clarke, an EA lead investigator, said: "In this case we have 17 landowners and communities blighted by significant amounts of dumped waste.
"We've already seen some of these sites catch fire, causing significant impact on communities, the environment and our emergency services partners who have to tackle them."
In September, Liverpool City Council said it had been left with a £1m waste disposal bill after six incidents in less than four months at vacant industrial sites in Merseyside.