The dead were identified as Raisingh Choudhary, 38 and Rahul Prasad, 20, the company said in a statement on Sunday, which added the fire has now been brought under control. Both were contractors working in the terminal.
"The fire which broke out in the Motor Spirit (MS) tank of IOC's bulk storage terminal at Hazira yesterday afternoon has been fully contained now and is only smoldering. All other tanks are safe," the company said.
Petroleum and Natural Gas Minister Veerappa Moily, who visited the site, said the damage to Indian Oil could be as much as 450 million rupees.
The company said the cause of the fire was being investigated by an internal committee which will submit its report on January 20.
The Hazira terminal has nine storage tanks - five gasoline and four diesel.
The tank where the blaze started had about 6,000 kilolitres of gasoline, almost half of its capacity, when it caught fire. Because of winds it had spread to another petrol tank.