"It has been reported that the chief officer, gas engineer, a bosun and three seamen were engaged in repairing a damaged pipe in the compressor room and were overcome by gas," a statement from the Directorate General of Shipping said in a late evening statement, adding five persons died in the accident.
The group of six sailors had gone into the compressor room while the Indian flagged vessel--MV Maharshi Krishnatreya-- was on its way to Dubai for dry docking after discharging cargo in Mangalore, a company official said.
All the six were found unconscious and help was sought from the authorities, the company official said.
In a statement, the Navy said it got a call from Varun Shipping at 1045 hrs, following which a Seaking MK 42C helicopter was sent from Mumbai for help.
The vessel was 140 nautical miles southwest of Porbandar when the Navy was informed, it added.
The company official said the rescue team, which included doctors, declared the five sailors dead while the sixth one was immediately rushed to Porbandar where he is receiving medical help.
However, when asked about the cause for the accident, the company official declined to specify reasons, citing pending investigations.
There was no explosion or fire on board and there has been no damage to the vessel either, the company official said.
When asked specifically if they would have inhaled something foul, the official said, "We need to figure it out... the compressor room is not locked per se, it has two doors."
There was a team of up to 20 sailors and officers, who was on board when the vessel was sailing, the official said.