The fire on MT Genessa, which is anchored 15 nautical miles off Deendayal Port Kandla, started around 6 pm on Wednesday.
The tanker is 183 metres in length and has a draft of 10 metres.
The Coast Guard is trying to fight the fire using tugs and rigs available from nearby resource agencies.
"There was a fire in the crew compartment and efforts are underway to douse it," a Coast Guard official said.
He said a Dornier aircraft has been pressed into service to ascertain the extent of the fire.
With inputs from PTI
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