The fire broke out at the coker unit of the refinery and flames could be seen from a distance of 10 km.
A company spokesperson confirmed the incident but said details were awaited and a formal comment would be made only after that.
Coker is the key driver to the high gross refining margins - the revenue a company earns on converting a barrel of crude oil into fuel - for the company.
Coker converts fuel oil into high value products like diesel and naphtha and the incident has the potential of derailing the refinery's gasoline and gas oil (diesel) production.