All 18 sailors onboard an Indian Navy submarine are feared dead after a huge explosion and fire rocked the vessel in its home port of Mumbai early Wednesday.
The blast killed some of the sailors on board, Defense Minister A.K. Antony said, without providing further details.
"It's a loss to all of us. It's a tragedy," Antony told reporters before leaving for Mumbai to assess the situation.
An Indian naval official, speaking on condition of anonymity, told the Associated Press that the navy believes there is no way anyone could have survived the intensity of the explosion and fire.
Navy divers had opened one of the submarine's hatches but had not yet been able to enter the submarine because it was dark and full of muddy water.
Local TV news station Headlines Today showed video of the explosion on the diesel-powered submarine, apparently filmed by a bystander. An enormous ball of red and yellow fire rose hundreds of feet into the air.
After the fire, the sub, identified as the Indian Naval Ship (INS) Sindhurakshak, was submerged at its berth in the naval dockyard with only a portion visible above the surface. The 16-year-old submarine had recently returned from Russia, where it was made, after undergoing an overhaul and upgrade, Rahul Bedi, an analyst for the independent Jane's Information Group, told the Associated Press.
India has 14 diesel-powered submarines, Bedi said.
One man standing outside the dockyard who declined to give his name said he heard a sound like a rocket or jet engine, then a blast. Another witness said the sky turned red after the explosion. Nearly a dozen fire engines rushed to the dockyard to douse the fire.
The fire was extinguished in about two hours, but a navy official said it was unclear how many sailors were killed or injured. The official spoke on condition of anonymity because he was not authorized to talk to reporters.
The official said that when the blast occurred, some sailors of other nearby units jumped into the sea in panic. He says some were injured and hospitalized.
Navy spokesman Narendra Vispute said the cause of the explosion was being investigated. The incident took place one day before India's Independence Day celebrations, and authorities have been on high alert for possible terror attacks.
The Sindhurakshak also suffered an explosion in 2010 that killed one sailor and injured two others. The navy said that accident was caused by a faulty battery valve that leaked hydrogen, causing an explosion in the vessel's battery compartment.
Last year, India acquired a Russian Nerpa nuclear submarine for its navy on a 10-year lease from Russia at a total cost of nearly $1 billion.
On Saturday, India activated the atomic reactor on its first indigenously designed and built nuclear submarine, which the navy could deploy in the next two years.
India has steadily built up its naval capabilities in recent years, spurred by its rivalry with neighboring China.
The Associated Press and Reuters contributed to this report.