A 30ft high pile of tyres and various metals were well ablaze when firefighters from Hindley and Atherton arrived at the site on Bolton House Road, Bickershaw, at 9.30pm on Thursday January 20.
Because of the sheer size of the waste mountain, the metallic materials involved and the difficulty in getting water at the bottom of the road, it took the crews two and a half hours to douse the flames.
Hindley watch manager Paul Gibbons said: "We are certainly not ruling out deliberate ignition here which makes it doubly annoying that we had to spend so long putting out the fire.
"Fire service resources were tied up for a considerable time and that was time that could have been spent at other emergencies.
"We are conducting investigations with the Environment Agency and hope that we can ensure that this does not happen again. It is not the first time we have been to this site."
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