The Environment Agency (EA) and the police have carried out a series of dawn raids as part of an investigation into illegal dumping of waste.
Following the dumping of up to 25,000 tonnes of material at 17 sites across the Midlands and northern England, five addresses were raided in Staffordshire, Herefordshire and Hertfordshire.
More than 25 EA investigators, supported by 20 police officers from the Staffordshire, West Mercia, Warwickshire and Hertfordshire forces were seeking evidence as part of Operation Cesium.
Two people were arrested while a third person is helping with enquiries.
The EA says the investigation is expected to continue for several months.
Paul Clarke, lead investigator for EA’s team, 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.”