Two Indian sailors were found dead Thursday a day after the submarine they were on filled with toxic smoke, authorities said.
The accident, the latest in a series of problems plaguing the Indian fleet, prompted the chief of the country's navy to resign.
Seven crew members of the Russian-built submarine, the INS Sindhuratna, have been hospitalized after inhaling smoke emanating from one of the vessel's compartments early Wednesday while it was off the coast of Mumbai, the navy said.
Two other sailors on the submarine had been reported missing. Their bodies were found Thursday in a smoke-affected compartment of the vessel, authorities said.
Adm. D.K. Joshi, the navy's chief of staff, stepped down Wednesday after news of the problems on the submarine emerged, the government said.
Joshi took "moral responsibility for the accidents and incidents which have taken place during the past few months," the defense ministry said in a statement.
The Indian navy declined to provide an exact number of how many incidents had taken place on vessels in recent months, saying only that there had been "a couple of serious accidents involving submarines."
In August, an explosion and fire sank another of India's Russian-made submarines, the INS Sindhurakshak, killing all 18 sailors on board. That was the navy's deadliest peacetime disaster.
The cause of the smoke Wednesday on the Sindhuratna is still under investigation, the navy said.
The Indian navy has been struggling to modernize its aging submarine fleet, which, like much of the Indian military, relies heavily on Russian hardware.
Analysts say the current number of submarines is far fewer than India needs to patrol is lengthy coastline, but plans to update the fleet have been held up because of technical problems, bureaucracy and higher-than-expected costs.