A digger was used to find the seat of the fire
Britain's second biggest tyre dump has been given contaminated land status - the same day firefighters tackled a massive blaze on the site.
At its height, six crews tackled the fire at Hampole Quarry, near Doncaster.
The site is home to between three and five million tyres, dumped over the past 30 years.
The Environment Agency said the blaze, within a pile of 1,000 tyres, had the potential to become a major pollution hazard.
Area manager Paul Tullett said: "The consequences, if the main body of those tyres was to catch fire, would be disastrous for the environment.
"As well as significant problems with smoke, there would be the potential for major pollution of the underground water supply beneath the quarry that, in turn, could pollute nearby rivers and streams."
The fire broke out on Tuesday at the abandoned tyre dump.
A digger was brought in by South Yorkshire Fire Service to help crews get to the seat of the fire, which was under layers of melted rubber.
Contaminated land status means Doncaster council can secure government funds to pay for the clean up of the site.
It was agreed after months of negotiations between the Environment Agency and the council.
Agency officers will continue to monitor nearby Hampole Dyke and Ea Beck for pollutants.