Approximately 60 to 70 scrap cars are on fire at a scrapyard on Doncaster Road in the Consibrough area of Doncaster.
Firefighters were called to the incident at 4am on Thursday morning. Around 25 firefighters with five fire engines from Edlington, Maltby, Dearne and Rotherham stations are at the scene.
There are no reports of any casualties.
Local residents are being asked to keep doors and windows closed.
A full fire investigation will be carried out once the fire has been extinguished.