KHABAROVSK, February 11 (RIA Novosti) - An Indian delegation has visited the dock in Russia's Far East where the Nerpa nuclear submarine has been kept since a fatal accident on board last year, the dockyard's director said on Wednesday.

On November 8, while the Nerpa submarine was undergoing sea trials in the Sea of Japan, its on-board fire safety system went off, releasing deadly gas into the sleeping quarters. Three sailors and 17 shipyard workers were killed. There were 208 people, 81 of them sailors, on board the vessel at the time.

India has reportedly paid $650 million for a 10-year lease of the 12,000-ton Nerpa nuclear attack submarine. Indian media have reported that the construction of the vessel was partially financed by the country's government.

"During their two-day visit to the Vostok dockyard, the Indian delegates inspected the submarine and met with experts employed at the dock," Gennady Bagin said adding that the delegation had already left for Vladivostok.

According to RIA Novosti sources, the Indian delegates are planning to visit the headquarters of Russia's Pacific Fleet in Vladivostok.

An ongoing investigation has supported the conclusion that the tragedy was caused by the mishandling of a temperature sensor on board which led to deadly Freon gas being released.

A serving crew member on the Nerpa, Dmitry Grobov, has been charged with "involuntary manslaughter" and may face a sentence of up to five years in prison.

The accident on K-152 Nerpa, an Akula II class nuclear-powered attack submarine, was the Russian Navy's worst since the sinking of the Kursk nuclear submarine in 2000, which claimed the lives of all 118 personnel on board.