MOSCOW (Reuters) -- Russian prosecutors have opened a criminal case against a sailor suspected of triggering an accident on a Russian nuclear submarine that killed 20 people at the weekend.
Prosecutors said the accident, which occurred during sea trials of the "Nerpa" nuclear submarine on November 8 in the Sea of Japan, was caused when the fire-extinguishing system was turned on, releasing freon gas that asphyxiated the victims.
"The suspect is one of the sailors in the crew who, without any reason whatsoever, turned on the submarine's fire-extinguishing system, as a result of which 20 people were killed and 21 hospitalized," the Prosecutor-General's main Investigative Committee said in a statement. "A criminal case in relation to the suspect has been opened under a clause in the Russian Federation's Criminal Code...causing death by carelessness of two or more people."
The suspect has confessed, the committee said. It did not say if it would be investigating why the activation of the fire-extinguishing system proved fatal for so many people.
Submarine crews are supposed to have breathing apparatus with them at all times to protect them from the gas. Freon is used as a fire suppressant.
The submarine accident, the worst since 118 sailors died in 2000 when the "Kursk" nuclear submarine sank in the Barents Sea, exposed the gap between the Kremlin's ambitions and its military capabilities.
The Russian Navy said 208 people -- or nearly three times more than its usual crew -- were on board the submarine.
Former submarine officers have said there may not have been enough breathing kits for all the people on the submarine when the gas was released.