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  • Story Highlights
  • 20 killed on Russian submarine were poisoned by fire safety system, officials say
  • Russia’s navy says the new nuclear-powered sub has returned to its base
  • Accident did not affect sub’s reactor; radiation levels on ship normal, reports say

MOSCOW, Russia (CNN) — An accident that killed 20 people on a new Russian nuclear submarine was caused by a malfunctioning fire safety system that spewed out chemicals, according to an initial investigation, officials said Sunday.

At least 21 other people were injured during Saturday’s test run in the Sea of Japan, the Russian Defense Ministry said.

It was Russia’s worst naval accident since the nuclear submarine Kursk sank after an onboard torpedo explosion on August 12, 2000, killing all 118 crew members.

The latest fatal accident was the result of the “accidental launch of the fire-extinguishing system” on the Pacific Fleet sub, Russian navy spokesman Capt. Igor Dygalo told reporters.

Russian news agency Interfax said a preliminary forensic investigation found that the release of Freon gas following the activation of the fire extinguishing system may have caused the fatalities.

Seventeen of the fatalities were civilian members of the shipyard crew, Interfax reported. The submarine was being field tested before it became a official part of the navy, according to a Russian Defense Ministry statement.

The statement said 208 people, including 81 soldiers were on board the submarine. In addition to the fatalities, the accident wounded 21, Russian officials said.

The accident did not damage the nuclear reactor on the submarine which later traveled back to its base on Russia‘s Pacific coast under its own power, Dygalo added.

The submarine returned to Bolshoi Kamen, a military shipyard and a navy base near Vladivostok, state-run Rossiya television said, according to The Associated Press.

Officials did not reveal the name of the submarine, but Russian news agencies quoted officials at the Amur Shipbuilding Factory who said the submarine was built there and is called the Nerpa.

Construction of the Nerpa, an Akula II class attack submarine, started in 1991 but due to a shortage of funding was suspended for several years, the reports said. Testing on the submarine began last month and it submerged for the first time last week.

The Kremlin is seeking to restore Russia’s military power amid strained ties with the West following the war with Georgia.

But despite former President Vladimir Putin increasing military spending, Russia’s military remains hampered by decrepit infrastructure and aging weapons.

The Kremlin said President Dmitry Medvedev was told about the accident immediately and ordered a thorough investigation.

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