No one was injured in the accident, IOC said in a statement.
"The cause of the fire is being investigated," it said.
Operations at all other units of 15 million tonnes a year Paradip Refinery are normal, IOC said.
"A minor incident of fire took place in the FCC-Indmax Unit at around 11.15 am today. The fire was put out immediately," the statement said. "There has been no injury to personnel or damage to property due to the incident."
IOC did not say if the fuel production would be impacted by the fire.
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