20 people have been killed and 22 injured in an accident on a Russian nuclear submarine in the Sea of Japan.
Autopsies showed the victims died from inhaling Freon gas released into part of the submarine when its fire extinguishing system activated for reasons that remain unclear.
The nuclear reactor that powers the submarine was not damaged and background radiation levels in the naval testing zone where the accident occurred were 'normal', a naval spokesman has said.
The high-speed attack submarine was undergoing sea trials.
It is thought to have been under construction since the early 1990s, its construction bogged down in the wake of the collapse of the Soviet Union.
State media said the vessel had been due to be delivered to India's navy.
Officials said three naval officers and 17 civilians had died in the accident.
The injured were evacuated from the stricken submarine aboard an accompanying ship and were taken to a hospital on shore for treatment.
The submarine itself returned to the port of Bolshoi Kamen, site of a large refitting shipyard.
