The fire and resultant smoke in the INS Sindhuratna started on the mess deck and not in the battery pits of the submarine, the Defence Ministry said here Tuesday, a week after the February 26 tragedy in which two naval officers were killed.
This was the conclusion of a preliminary investigation into the incident by a board of inquiry headed by a two-star admiral.
After the submarine returned to the Mumbai harbour, another specialist team of Western Naval Command headquarters also carried out an investigation.
Two officers - Lt. Commander Kapish Muwal of Najafgarh, Delhi, and Lt. Commander Manoranjan Kumar of Jharkhand - lost their lives while seven naval personnel were injured in the incident that led to the resignation of Chief of Naval Staff Admiral D K Joshi.
"Based on preliminary inspection of the third compartment, the likely seat of the fire has been indicated at the mess deck located one deck above the battery pit. Certain electrical cables were observed to be burnt or damaged in this area," the Defence Ministry said.
However, the cause of the fire in the location - which was the sailor's accommodation area - would be ascertained in due course by the board of inquiry.
The Sindhughosh-class of submarines carries 240 cells, distributed equally in forward and aft battery pits. The batteries currently installed on INS Sindhuratna have completed around 113 cycles till date of their 200-cycle life.
"The life of the batteries is valid by date. The batteries which were being used by INS Sindhuratna at the time of the incident were, therefore, operationally in-date," naval officials said.
A preliminary inspection of the battery pit and the batteries in it revealed that there was neither any damage nor any sign to indicate that the fire could have originated there.
As the batteries appear to be clear of any damage, they would not be put through normal checks and maintenance routines prior to operationalisation, the officials said.