Ten fire engines and more than 50 firefighters have been tackling a fire at Tata Steel on Aldwarke Lane, Rotherham, overnight.
It involved several thousand litres of oil. Officers say their teams quickly contained the blaze to one building.
All employees have been safely evacuated and there are no reports of anyone being injured.
Crews used a high volume pump to access water from an on site reservoir.
It broke out shortly after 1.00am on this morning.
Fire engines from Rotherham, Parkway, Central, Elm Lane, Edlington, Dearne, Birley Moor, Stocksbridge and Tankersley stations were involved.
South Yorkshire Fire and Rescue say the fire is now out and their firegithers have left the scene.
An investigation into its cause will begin once it has been fully extinguished.