The circumstances that led to the emergency landing were not immediately clear.
Four people have died after a helicopter carrying seven passengers and two pilots today fell into the Arabian Sea while attempting to land at the Oil and Natural Gas Corporation Limited (ONGC) Sagar Kiran rig at Mumbai High. All nine people were pulled out after successful rescue operations but four have now been reported dead. The helicopter was a newly leased Pawan Hans Sikorsky S-76.
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, news agency PTI said. Three of the four who died were ONGC employees.
The chopper was attempting to land at the rig, located some 111 km west of 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, an official said.
A rescue boat from the rig Sagar Kiran, near which the helicopter made the emergency landing, rescued at least one person, the official said.
Five people were rescued by Offshore Supply Vessel Malviya-16 which was diverted by MRCC Mumbai to join rescue operations.
A Coast Guard ship at sea was diverted to reach the spot, and another ship sailed out from Mumbai to join rescue operations, officials said. A Coast Guard aircraft dropped a life raft for survivors.
International Safety Net (ISN) has been activated by the Maritime Rescue Coordination Centre (MRCC), Mumbai. The Coast Guard is coordinating with the Indian Navy and ONGC for mobilisation and augmentation of the rescue effort, officials added.
The circumstances that led to the emergency landing were not immediately clear. Other details too were awaited.
ONGC has several rigs and installations in the Arabia Sea that are used to produce oil and gas from reservoirs lying below the seabed.