Report: Fire system problem led to deaths

MOSCOW, Nov. 10 (UPI) -- A malfunction in the fire safety system was the probable cause of the deadly accident aboard a Russian submarine, an investigatory commission said Monday.

"The preliminary official conclusion is the unauthorized operation of the fire extinguishing system," Ksenia Gusentsova, spokeswoman for the chief federal inspector for the Primorye Territory in Russia's Far East, told RIA Novosti.

Tuesday was declared a day of mourning in Primorye Territory, base of the Russian navy's Pacific Fleet.

The weekend incident killed 20 people and injured 22 while the Nerpa nuclear-powered sub was conducting exercises in the Sea of Japan. Investigators said the dead were suffocated when Freon gas was released after the vessel's fire safety system was activated.

A Russian naval commander said earlier the submarine's reactor wasn't affected by the incident and radiation levels were normal.

The incident is the worst for the Russian navy since the Kursk submarine sunk in 2000, killing all 118 members of its crew.