An explosion rocked an Indian Navy submarine docked in Mumbai early on August 14 and caused the boat to sink with 18 sailors trapped inside.
An Indian navy official said that other sailors were working frantically to save them.
Defense Minister AK Antony said that Navy personnel have died, but gave no details.
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.
The explosion, which happened around midnight local time, was accompanied by a fire; the sub was docked in the high security naval dockyard in the city.
The vessel is powered by diesel and electricity. After the fire, the sub was submerged at its berth in the naval dockyard with only a portion visible above the surface.
Journalist Anurag Tripathi said that “many sailors jumped off after [the] explosion.” The 18 sailors were still trapped inside when the boat sank around 7:47 AM IST (10:17 EDT).
The explosion was initially reported by Indian journalists and media more than 6 hours earlier.
The injured sailors were taken to INHS Ashwini, an Indian Navy hospital.
The fire is extinguished.
The cause of the explosion and fire is undetermined as of yet.
Sources told NDTV that the submarine was fully armed when the explosion happened in the weapons bay, and the fire resulted in the detonation of torpedoes and/or missiles on board.
The Navy has ordered a board of inquiry into what happened, reported the Hindustan Times.
The 16-year-old Russian-made submarine, INS Sindhurakshak, had recently returned from Russia after undergoing an overhaul and upgrade, Rahul Bedi, an analyst for the independent Jane’s Information Group, said.
India has 14 diesel-powered submarines, he said.
The INS Sindhurakshak had previously had a fire accident on February 26, 2012, which killed one sailor and injured two others, said Tripathi.
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.
Story developing; check back for updates.
The Associated Press contributed to this report.