Two men have been arrested over a 21,000-tonne, 500ft-long fly tip that appeared in a field.
The vast illegal dump near Kidlington in Oxfordshire sparked widespread outrage and will cost the Environment Agency around £10million to clear.
Today, the EA said a 69-year-old man had been arrested at a home in Andover, Hampshire, while a second man, 54, was arrested in Slough.
Both are accused of environmental and money laundering offences relating to the giant tip.
The arrests are part of an ongoing investigation and both men have been released on bail.
The mega tip in Oxfordshire, sat between the River Cherwell which later joins the Thames and the A34, is made up of processed domestic waste, such as shredded plastics, polystyrene, and other household items.
It is believed the waste was dumped in one go and it has since been described by an MP as ‘threatening an environmental disaster’.
It is not known when exactly the mountain appeared but the EA was alerted in July last year, while horrified amblers became frustrated at the apparent lack of action by authorities as the months passed.
The Kidlington site is just one of 517 illegal dumps across England – at least 11 of which are classified as ‘super sites’ because they contain over 20,000 tonnes of waste.
Among them are a 280,000 tonne site in Cheshire, two 50,000 tonne sites in Lancashire and Cornwall, and a 36,000 tonne tip in Kent.
Most of the illegal sites are in countryside locations, where they are hidden on what should be greenbelt land, and are usually run by organised criminal gangs, police said. The gangs make money by charging significantly less than official operators to take and bury waste.
Two men were arrested on Thursday as part of an ongoing investigation into a 21,000 tonne fly tip in Oxfordshire
Police officers raiding a house during one of this morning’s operations
The 20ft-high pile of hazardous rubbish was illegally dumped in a field next to the A34 and River Cherwell near Kidlington in Oxfordshire
The beginning of the clear up operation was started earlier this month as concerns about fire and the impact on the nearby A-road were raised.
A private waste clearance firm was given a £9.6million contract to deal with the site over the next year.
Emma Viner, enforcement and investigations manager for the EA’s national environmental crime unit, told the BBC the agency would be looking to recover the clearance costs under the Proceeds of Crime Act from anyone prosecuted for the illegal tip at the end of its ongoing investigation.
Ms Viner said: ‘The illegal dump at Kidlington was an atrocious and deliberate attack on our environment and the Environment Agency shares the community’s anger at this horrific crime.
‘The illegal dumping of waste at Kidlington is appalling and has caused significant damage to the environment and distress to the local community.
‘The government is committed to stamping out this type of criminality across the country, by boosting funds to tackle waste crime, hiring more officers and introducing tougher checks and penalties for those who break the law.’
The arrests made on Thursday by officers from the South East Regional Organised Crime Unit (SEROCU) followed the arrest of a 39-year-old man from Surrey in November, who was released pending further investigation.
The 500ft-long dump has been described as one of the biggest fly-tips ever seen in Britain
The mountain of toxic waste sits on greenbelt land adjacent to both the A34 dual carriageway and the River Cherwell, which later joins the Thames
The issue gained political traction last year, with Calum Miller, Liberal Democrat MP for Bicester and Woodstock, raising the issue in Parliament in November.
Addressing MPs, he said: ‘Criminals have dumped a mountain of illegal plastic waste… weighing hundreds of tonnes, in my constituency on a floodplain adjacent to the River Cherwell.
‘River levels are rising and heatmaps show that the waste is also heating up, raising the risk of fire.
‘The Environment Agency said it has limited resources for enforcement, that the estimated cost of removal is greater than the entire annual budget of the local district council.’
Responding, environment minister Mary Creagh said Labour inherited a ‘failing’ waste system that has caused an ‘epidemic of illegal fly-tipping’.
