The Indian government Monday said that preliminary probe into the submarine tragedy indicated the multiple explosions on INS Sindhurakshak, which triggered a huge fire and gutted the Russia-made vessel, killing 18 sailors, were due to the \"possible ignition of armament\". \"Preliminary investigations indicate that the explosion was due to the possible ignition of armament. The cause of ignition is, however, yet to be established. Forensic examination would throw more light into the possible cause of ignition,\" Indian Defense Minister A.K. Antony told the Parliament. The Defense Minister said that the \"rapidity and intensity of the explosions and the resultant damage to the submarine indicate that the 18 personnel on board would not have survived.\" Claiming that international agencies have been approached for salvage operations of the sunken submarine, which was loaded with missiles and torpedoes, Antony said: \"There is also an offer of help from Russia, where the refit and upgrade of the submarine had been undertaken.\" Indian Navy divers have so far been able to recover bodies of six sailors, out of 18 who were on board the submarine when the tragedy happened at Mumbai naval dockyard in the early hours of Wednesday. \"Search is still on to find the 12 other sailors feared dead in the tragedy amid fears that the bodies of other sailors could have melted due to high temperature within the vessel following the explosions,\" said naval sources Sunday. The Indian Navy had last week ordered a high level probe into the incident, which took place a day before India\'s Independence Day and only two days after India launched its first indigenous aircraft carrier, hailed as a \"crowning glory\" by naval officials. A similar explosion in the same submarine in 2010 claimed the life of one sailor. The vessel was at the time berthed at Visakhapatnam port in the southern Indian of Andhra Pradesh. The 16-year-old INS Sindhurakshak is one of the 10 kg class submarines bought from Russia and equipped with the Russian Club-S cruise missile system. India had three months back spent some 80 million U.S. dollars to upgrade it in Russia and it\'s expected to serve Indian Navy for 10 more years.