At least 8 people were killed after a cruise ship "Bulgaria" carrying 185 people sank in Volga river Sunday and the chances to find the nearly 100 missing are "very small," according to the Russian Emergencies Situations Ministry.

Russian Emergencies Ministry members search for the missing people from a tourist boat that sank on the Volga river in the Tatarstan region July 10, 2011. [Agencies]

The double-decker vessel went down some 3 kilometers (2 miles) away from the nearest bank in the giant Kuibyshev reservoir on the Volga River some 450 miles (750 kilometers) east of Moscow, the Tatarstan region emergency ministry said. The depth at the site was 20 meters (65.62 feet), it said.

Some 30 children gathered in one of the cockpits minutes before the sinking, another survivor told the Interfax news agency.

Emergency teams and divers from neighboring regions rushed to the site of the tragedy, and Tatarstan's leader Rustam Minnikhanov interrupted his vacation to return to the region.

According to the latest news from the Russian Emergencies Situation Ministry, there were 185 people aboard the double-decker ship, 80 of them have been rescued, while 103 others were still missing.

The ministry spokeswoman Irina Andrianova said chances of finding more survivors were "very small."

Earlier, the ministry said there were 188 people aboard the ship, 85 of them have been rescued by a passing ship "Arabella", 102 others were missing.

The Kremlin press office said Russian President Dmitry Medvedev has held phone conversation with Emergencies Situation minister after the accident and ordered an investigation into the accident.

The president also ordered Tatarstan head Rustam Minnikhanov to give assistance to the survivors and victims and their families.

The boat, called Bulgaria, was built in 1955 in Czechoslovakia and belongs to a local tourism company. It was going to the regional capital, Kazan from the town of Bulgar.

According to local media reports, three factors may have caused the accident, including the violation of ship's operation, overload, and aging of the ship.

"It case of an accident these ships sink within minutes," Dmitri Voropayev, head of the Samara Travel company told the Ria Novosti news agency.