A vessel carrying sand, steel and other cargo from Calcutta to Port Blair sank in the Bay of Bengal on Sunday afternoon, with its captain and two other crew members missing till late on Monday night.

Eleven others were rescued from the choppy waters by the Indian Coast Guard.

Pervez Rahman, owner of the MV ITT Puma, identified the missing captain as Sudam Debnath, who is from Calcutta. The Mumbai-registered vessel operates under an Indian flag.

“The search for the missing three is still on and so the rescue vessels are unable to return to the coast,” a coast guard official said on Monday night.

He said the sea was “extremely rough” and it was raining heavily. “The choppy waters and extremely poor visibility have made the rescue operation difficult and risky.”

The 1982-built general cargo vessel sank 90 nautical miles (167km) south of Sagar Island. The rough seas had caused the cargo to shift to one side, tilting and eventually sinking the vessel, the coast guard said.

ITT Puma, with a capacity of 2,200 tonnes, was carrying around 1,900 tonnes of cargo, Rahman said.

The coast guard’s maritime search and rescue coordination centre in Chennai had received a distress email from the shipping company at 4.25pm on Sunday and forwarded it immediately to the coast guard’s Haldia unit.

Usually, vessels have search-and-rescue transponders that are connected to the shipping company which, in turn, sends the distress signal to the nearest coast guard base, an official said.

“Responding to the distress call, Indian Coast Guard regional headquarters, northeast, directed two vessels and a Dornier aircraft for the search and rescue efforts,” a coast guard official said.

The Dornier spotted the ITT Puma around 6.30pm on Sunday. “The aircraft, with night-vision-capable sensors, detected two life rafts adrift,” the official said.

From their life rafts, the crew of the sinking vessel spotted the aircraft and fired red flares, which the Dornier detected. Two coast guard vessels were dispatched for rescue.

The coast guard’s fast patrol vessel, Amogh, and advanced off-shore patrol vessel, Sarang, reached the spot around 9pm, the official said. “The rescue vessel found the two rafts with orange canopies tied together,” he added.

The survivors were waving their arms desperately and using whistles as signals.

The rescue began late on Sunday and continued till early Monday.

“An unprecedented, extensive sea-air coordinated operation resulted in the safe rescue of 11 crew members,” the coast guard official said.

The crew were offered medical assistance on board the two vessels.

Pictures taken from the Dornier showed the entire cargo vessel in the night sea. Late on Monday, only its tip could be seen from the sky as it had sunk further.

“It (the vessel) had set off from Calcutta for Port Blair on the night of August 24. Itwas carrying sand, steel and containers,” owner Rahman said.

The vessel would make at least three trips in two months to the Andamans carrying general cargo. “It had never faced any problem earlier. This time I heard the sea was extremely rough,” Rahman said.

Calcutta Port Trust sources said the vessel had sailed past the Sandheads near Sagar Island and was in deep sea when it sank.