Monisha Rockett shared an image of a road in Sprotbrough, to the north of the town centre, with 'ash falling from the sky'.
The fire has also spread to the garden of a house beside the tracks.
Monisha said: "Hope everyone's OK in Sprotbrough. It was just orange darkness driving through then. Ash falling from the sky."
Sprotbrough Road has now been closed.
Another witness, Lianne Arnison, added: "Hope everyone is OK. Huge respect to our fire brigade and emergency services trying to tackle this! Looks like three fires that are reigniting and moving along in the wind."
Another Facebook user shared aerial images of a large area of farmer's fields on the other side of the railway that had been destroyed.
The Newton Arms pub has been forced to close and shared video of the flames creeping close to the children's play area. They posted: "The emergency services are on their way and in the interests of public safety we have taken the decision to close the Newton Arms this afternoon. Please keep an eye on this page for any updates and please keep yourselves safe."
Doncaster Council said: "A section of Sprotbrough Road is currently closed due to a large fire in the area. A diversion will be in place soon, and resident access will be granted as soon as possible.
Sprotbrough resident Kate-Elisia Mynett said: "Update - our fence has gone, our next door neighbours' shed has gone up and most of their garden, and our conservatory has started to melt and there is no power. My dad is helping the fire brigade along with other residents of Sprotbrough Road.
"Been evacuated by the police now behind my house and the house is full of smoke and raining ash in front and back garden."
Fire crews in Doncaster are also fighting major fires in the Hatfield and Rossington areas.
South Yorkshire Police and British Transport Police have been contacted for updates.