A Malaysian cargo ship sank in the Bay of Bengal, some 300-km south of its destination of Kolkata Port on Tuesday.
A Coast Guard rescue team picked up eight sailors from the high seas after MV Genius Star-VI went down carrying a cargo of logs.
"We are still searching for the missing nine crewmembers," Coast Guard's eastern sector chief R.K Wadhwa said.
The ship was registered in Panama and all members of the crew were Chinese nationals.
The ship began listing on its side on Tuesday morning and sank around afternoon.
"We still don't know what caused the accident, but it could have been because the ship was old," Wadhwa said.
A Coast Guard aircraft and two rescue vessels were looking for the missing sailors.