The bodies of four people have so far been fished out of the sea, near the debris of the helicopter.
Five ships, two Dornier and two helicopters have been deployed for search and rescue operations.
The ONGC, along with the ICG and the Indian Navy, has pressed its helicopter and speedboats for search operations.
"Two Immediate Support Vessels (ISV)s deployed for patrolling in the area have been diverted for search and rescue operations along with three Coast Guard units. Seaking 42B helicopter is being launched in addition," a Navy spokesperson said.
The helicopter, V T PWA Dauphin, which took off from Juhu at 10.20 am, was scheduled to land at North Field of the ONGC at 10.58 am.
The last contact with the Air Traffic Control (ATC) was made at around 10.30 am, 30 nautical miles off Mumbai.
The cause behind the tragic incident is not yet known.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)