An agricultural waste fire will be left to burn because putting it out would have “a much greater impact on local wildlife and water sources”, according to the fire service.
Crews were first called to the blaze on Howbrook Lane in Wortley, on the border between Barnsley and Sheffield, on Saturday night.
South Yorkshire Fire & Rescue Service said there was no risk to nearby homes or people and the fire was not expected to spread.
Following specialist assessment, the service said partner agencies had agreed “the safest approach is to allow the fire to burn under close monitoring.”
It said: “Extinguishing it with water would cause polluted run-off into a nearby brook, ponds and a reservoir.
“This would create a much greater impact on local wildlife and water sources.
“The fire may continue to burn for several weeks, during which time we will keep this under review.”
The service said smoke from the blaze may cause concern for residents and urged anyone affected to keep windows and doors closed.
“We remain in close contact with local partners and will review our tactics if needed,” it added.