A police in Russia's Volga Federal district opened on Sunday a criminal case into a cruise ship's sinking that killed one person and left over 80 missing, Russia's Investigative Committee said in a statement.
The case was opened on safety violation charges.
The Kremlin said that the Russian President Dmitry Medvedev ordered the Investigative Committee's Chief, Alexander Bastrykin to "create an investigative team in order to establish a cause of the tragedy and find those responsible for the accident."
The double-deck cruise ship Bulgaria, en route from the Tatar town of Bolgar to Kazan sank at 13:58 Moscow time (09:58 GMT) on Sunday near the village of Syukeyevo in the Kansko-Ustinovsky district of the Republic of Tatarstan.
Russia's Emergencies Ministry said there were 182 people aboard the ship, including 125 passengers, 22 crewmembers and 35 staff workers.
Earlier, the regional emergencies center reported about 173 people on board the sunken ship.
According to the latest information, 84 people have been rescued, one woman had died and 97 are still missing.
The Emergencies Ministry's Il-76 jet with rescuers and salvage divers on board was dispatched to Tatarstan, a ministry's spokeswoman said, adding that 80 people and 22 rescue units are involved into the operation.