An explosion resulting in a major fire took place on board INS Sindhurakshak, a Kilo class submarine of the Indian Navy, shortly after midnight.
In Pictures: Explosion on board INS Sindhurakshak
Fire tenders from the Naval Dockyard as well as the Mumbai Fire Brigade were immediately pressed into action.
However, due to as yet unknown damage suffered as a result of the explosion, the submarine has submerged at her berth with only a portion visible above the surface.
About 18 persons were on board the submarine at the time of the accident and efforts are on to ascertain the safety of the personnel and salvage of the submarine.
The Navy has ordered a board of inquiry to probe the explosion and subsequent fire on board the submarine, a defence spokesperson said.
The submarine had returned after a major upgrade programme in Russia 3-4 months ago and is armed with a potent weapons package including the anti-ship Club missiles.
INS Sindhurakshak was not on active duty at the time of the accident, Navy sources said.
The incident has come at a time when the Navy is facing a situation of depleting submarine fleet. (With PTI inputs)