Sailors feared dead in Indian sub blast INDIA'S navy says all 18 sailors on board a submarine which exploded and sank are feared dead, and admitted the incident had left a "dent" in the country's defences. The fully-armed INS Sindhurakshak, returned by original manufacturer Russia earlier this year after a major refit, exploded in flames in Mumbai shortly in the early hours of Wednesday and sank in a military shipyard. The disaster is thought to be the Indian navy's worst since the sinking of a frigate by a Pakistani submarine in 1971. Defence Minister A.K. Antony described the explosion as the "greatest tragedy in recent time." "I feel sad about those navy personnel who have lost their lives in service of the country," he told reporters in New Delhi. Chief of naval staff D.K. Joshi said no sign of life had been detected on board even after divers managed to enter through the main hatch in a bid to refloat the vessel. "While we hope for the best, we have to prepare for the worst," he told reporters in Mumbai, adding that there was a possibility some crew might have found air pockets but "the indicators are negative. "It is certainly a dent on Indian navy's submarine capabilities for the time being," he added. The world's biggest democracy has been expanding its armed forces rapidly to upgrade its mostly Soviet-era weaponry and respond to what is perceived as a growing threat from regional rival China. Amateur video footage showed a fireball in the forward section of the Sindhurakshak, where torpedoes and missiles are stored as well as the battery units. "There were two to three explosions and the night sky lit up briefly," eyewitness Dharmendra Jaiswal told AFP. Joshi said there had been an initial fire which appeared to have sparked a big explosion as weaponry ignited. The basic question is what caused the fire and explosion. We do not have an answer to that question as of now," he said. A board of inquiry would probe all possible explanations including sabotage, but "the indicators at this point of time do not support that theory," he said. P.S. Rahangdale, an off-duty firefighter who rushed to the scene, told a local television channel that the Sindhurakshak "was totally on fire" and was berthed next to another submarine. "Because of timely intervention of my team and resources and navy's resources we could save that second submarine," he said. Other sailors on vessels berthed nearby were admitted to a navy hospital in Mumbai with burns. In February 2010, the Sindhurakshak suffered a fire while docked in Visakhapatnam city in southern India, killing a 24-year-old sailor and leaving two others with burns. A spokesman for the Russian Zvyozdochka company which overhauled the Sindhurakshak's weapons, navigation and power generator systems said India raised no objections about the vessel when it was returned after testing in April. The submarine, whose name means "Protector of the Seas" in Hindi, is still covered by a Russian warranty and eight Zvyozdochka employees are in Mumbai, the spokesman said. "Zvyozdochka is prepared to render its full assistance in the investigation and search for the causes of the accident," the spokesman told the ITAR-TASS news agency. The submarine was built in 1997 in Saint Petersburg and had completed 1000 dive hours since returning after its refurbishment. Rahul Bedi, a defence expert with IHS Jane's Defence Weekly, told AFP the 16-year-old submarine lacked some safety features common to newer vessels even after its $80 million overhaul. "They don't have escape routes in the event of accidents, unlike some of the modern submarines," he said.