Four persons, including 3 ONGC employees, died when a Pawan Hans helicopter with two pilots and seven others onboard fell into the Arabian Sea about 50 nautical miles from the Mumbai coast.

The helicopter managed to stay afloat with the help of the attached floaters for some time, helping rescuers pull out all the nine people, a company official said.

Four of them were unconscious and were airlifted in a Navy copper to a hospital in Mumbai, where they were declared dead, he added.

Earlier, it was reported that six of the nine persons so were brought to safety and attempts were on to rescue others, a company official said.

The helicopter, which had six ONGC personnel onboard, and one belonging to a contractor working for the company, was forced to land using the floaters that are attached to choppers that carry personnel and material from shore to offshore installations.

The chopper was attempting to land at the rig, located some 50 nautical miles from the Mumbai coast, when the incident took place. About 1.5 km from the landing zone on the rig, the chopper fell into the sea, the official said.

The circumstances that led to the incident were not immediately clear. Other details too were awaited, he said.

ONGC has several rigs and installations in the Arabia Sea that are used to produce oil and gas from reservoirs lying below the seabed.

ONGC deployed vessels from nearby installations to pull out the personnel onboard the helicopter.

A rescue boat from the rig Sagar Kiran, near which the helicopter made the emergency landing, rescued at least one person, the official said.