Oil patches spotted in areas up to 12 nautical miles from the spot where MV Rak sank.
There is a scramble to contain the oil spill from MV Rak that has triggered environmental concerns.
The Indian Coast Guard deployed one more ship and an aircraft to combat the oil spill off Mumbai coast after the Panama-flagged bulk carrier MV Rak sank.
ICGS Amrit Kaur has joined two other ships, Pollution Control Vessel Samudra Prahari, the ICGS Sankalp, for the pollution-control operations.
The ship sank 24 nautical miles off the Mumbai coast on Thursday and it started leaking oil on Saturday night.
Officials from the coast guard, west region headquarters, on Monday said the ship had about 290 tonnes of fuel oil and another 50 tonnes of diesel.
Earlier, coast guard officials had said that the ship had only around 100 tonnes of fuel oil in its tank
"The operation Paryavaran Surkasha launched for the pollution response could continue for two to three days more or it could even take a month depending on the leakage," said IG, coast guard, west region SPS Basra.
The coast guard officials also said that oil patches have been spotted in areas up to 12 nautical miles (around 22 km) from the spot where MV Rak sank.
On Sunday, coast guard ships used more than 700 kg of oil spill dispersant to contain the oil that spilled out of the sunken ship and around 2,600 kg of oil spill dispersant was used by Monday evening.
Due to the rough weather, coast guard officials are unable to make use of skimmers - rubbers sheets used to collect the oil and easing the mitigation.
On Sunday, around 1.5 to 2 tonnes of oil leaked in an hour but by Monday the leakage was around 1 tonne oil an hour.
The thickness of the oil sheen in the sea has reduced as compared to what it was earlier on Sunday.
Officials said that 100 tonnes of oil in the ship's tank had leaked and the remaining would leak in a day or two.
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