The explosion occurred when welding work was underway in an ethanol storage tank, the officials said, on the condition of anonymity as they were not authorised to speak with the media.
The cause of the incident is still unclear, they added.
IOC did not immediately respond to Reuters' requests for comment.
Officials are at the premises and are assessing the damages, the sources said, without providing details.
(Reporting by Varun Vyas in Bengaluru and Praveen Paramasivam in Chennai; Editing by Savio D'Souza and Sohini Goswami)
