Calcutta: Choppy waters on Sunday forced a salvage team aboard a tugboat to give up attempts to get close to the abandoned cargo ship that caught fire four days ago near the Sunderbans coast.

The team was approaching MV SSL Kolkata on a Calcutta Port Trust vessel when heavy shoaling in the Bay of Bengal - it is the effect by which surface waves entering shallower water change in wave height - forced them to turn back.

The Bay of Bengal is around eight nautical miles from the Sunderbans.

The cargo ship has been adrift in shallow waters since June 14, when the Coast Guard rescued its 22-member crew.

The salvage team comprising experts from the multinational company SMIT has been hired by Shreyas Shipping and Logistics, the owner of the cargo ship.

On Saturday morning, a navy team and three crew members of the MV SSL Kolkata had descended on the ship from a Sea King 42C helicopter. The team managed to drop the starboard (right) anchor of the ship that had till then been drifting towards the maritime border with Bangladesh.

Two officials from SMIT were airlifted by the Coast Guard in a Dornier aircraft for a close aerial survey of the ship, an officer said.

The Coast Guard will make an attempt on Monday to take the salvage team till the abandoned ship.

An officer in the Calcutta Port Trust said the fire had not yet affected the hold that contains chemicals. "Thick iron plates separate one hold from another. This is why the fire has not yet reached the cargo hold where the chemicals are kept. But we do not know how long the partition will work if the fire continues to rage."

There is also the danger of structural damage to the ship if the fire continues to burn.

No oil or chemical spill has been reported so far.

Two advanced offshore patrol vessels with fire-fighting and pollution response capabilities have been maintaining a round-the-clock vigil on the ship. Four hovercraft of the Coast Guard are on standby at the Fraserganj forward operating base to help the salvage team, if needed.

Three other Coast Guard vessels and pollution control equipment have been kept ready at the Haldia port for immediate deployment in the event of an oil spill.

MV SSL Kolkata was abandoned by its captain and crew after flames aided by strong winds spread to 70 per cent of the ship, then positioned about 55 nautical miles from Sagar Island.