A jury has dropped negligence charges against the captain of a Russian nuclear submarine in which 20 people died when a fire suppressant system was accidentally set off three years ago.
Seventeen of the dead were civilians, killed when fire-suppressant freon gas was released on the Nerpa attack submarine during sea trials in the Sea of Japan in November 2008.
Another 21 people were injured, in Russia's worst naval accident since the sinking of the Kursk nuclear submarine in 2000.
The Nerpa's captain, Dmitry Lavrentyev, and engineer Dmitry Grobov, who allegedly set off the sub's fire safety system "without authorization and for no reason," have been charged with professional negligence resulting in death or injury.
The jury at a naval court in the far eastern port city of Vladivostok acquitted the two men on Friday.
Naval prosecutors said they would appeal the decision.
"The jury did not acknowledge the fact of the release of the fire-suppressant mixture," a Pacific Fleet prosecutor said. "This is strange because this did happen."
The Nerpa was undergoing shakedown trials and had 208 people aboard, nearly three times its normal complement.
A former senior medical officer with the Pacific Fleet alleged in May the Nerpa's firefighting system contained a "lethal" mixture of freon and trichloroethylene - a commonly used industrial solvent which is highly toxic and corrosive - rather than pure freon.
Workers at the Amur Shipyard, where the submarine was built, said in an open letter in the same month that Lavrentyev and Grobov were "scapegoats" and that the disaster was the result of "corruption and disintegration of the military-industrial sector."
The Nerpa is due to be leased to the Indian navy in November.