Crews were first called to land near Kilner Bridge, Denaby Main, on Sunday at 4.15pm.
Several crews from Rotherham and Doncaster have kept returning to the site to keep the blaze under control.
Fire crews yesterday borrowed two 5,000 litre water bowsers from Doncaster Council's highways department to help tackle the blaze.
A spokeswoman said a crew from Dearne station had spent the day there today (Wednesday) and added: "We hope to be coming away soon."
An investigation into the cause of the blaze will be carried out once it has been extinguished.