Divers are continuing to search the wreck of the Bulgaria which had more than 200 people on board when it sank.
Around 80 people were rescued after the river cruiser sank around two miles from shore.
One survivor claimed other ships had refused to come to the aid of the stricken vessel.
The boat was heading to the regional capital, Kazan, around 500 miles (800km) east of Moscow.
Cruises on the Volga, which cuts through the heart of Russia and drains into the Caspian Sea, are popular among Russians as well as foreigners.
State television said the 50-year-old two-deck Bulgaria had dozens of cabins and two restaurants.
President Medvedev has ordered an investigation into the incident and declared Tuesday a day of mourning.
Medvedev also demanded a full technical assement off all 1,568 registered passenger ships.