One sailor, James Jacob, died in the accident that hit the Torpedo Recovery Vessel last night while 23 were rescued.
Four personnel were still missing. They include a Commanding-level officer, two divers and a crew member.
The vessel had sunk at 8 PM last night while it was on a "routine" mission to recover dummy torpedoes fired by fleet ships during a "routine" exercise, the Navy said.
Nine ships of the Eastern fleet and a few aircraft including Boeing P81, Dorniers, SKG 42C with night vision capabilities and Chetak helicopters have been deployed through the night to search for missing personnel, Navy spokesperson D K Sharma said.
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Citing preliminary information, the Navy sources said the "probable reason" for the sinking of the vessel seems to be ingress of sea-water in the Engine room and Aft Steering compartment. This, they said, could have been because one of the seals in the shaft gave way.
In view of the accident, Navy Chief Admiral R K Dhowan, who is on a four-day visit to Seychelles till November 9, is cutting short his visit to reach Visakhapatnam.