The Environment Agency is investigating after thousands of tyres were dumped in County Tyrone.
Up to 100 tonnes were left on land near Pomeroy. Arrangements are being made to have them disposed of properly.
The landowner claimed a relative had planned to build a go-kart track but many more tyres than expected had turned up.
He said he was unable to contact the relative and was not sure where they had come from.
It is believed that stricter controls in a key export market may have been increased the numbers of used tyres in circulation.
India was taking large volumes of tyres, but its government recently tightened up rules amidst concerns about the environmental impact.
That increased the cost for anyone here trying to dispose of used tyres and led an industry body to issue a warning about increased illegal dumping.
More than two million used tyres are produced by motorists in Northern Ireland every year.
About half are treated at Northern Ireland's only licensed recycling plant in County Antrim.
It turns them into a range of products including soft surfaces for council playgrounds and infill for engineering products.
When motorists buy new tyres, the cost includes a fee of about £2.50 for disposal of the used one.
The cost to the tyre seller is approximately £1.50 to have it removed and dealt with legitimately.
An industry body that represents tyre retailers said illegal dumping was a scourge carried out by "unscrupulous" people.
Dasos Michaelides, of the National Tyre Distributors Association, said it had been happening regularly in recent years, even at high profile tourist spots like the Giants Causeway.
He said tyre sellers and collectors had to comply with licence conditions to ensure waste tyres were dealt with correctly, but there needed to be much greater scrutiny.
"There's been some well-publicised cases of tyre dumping and we all understand the limited resources, but enforcement needs to happen - end of story, it really does need to happen.
"If someone unscrupulous turns up at your place offering to take your tyres away don't be fooled by a cheap price."