The Russian Emergency Situations Ministry said in a statement Wednesday that some 200 divers are still scouring the river for bodies.
A total of 208 people are believed to have sailed on the 55-year-old double-decker boat, the Bulgaria, that officials say was overloaded when it sank.
They have not yet determined the cause of the sinking. Survivors reported the boat was listing to starboard and having engine trouble even as it left the town of Bulgar en route to Kazan, about 750 kilometers (450 miles) east of Moscow.
Families of the victims were burying their relatives at the multi-faith Kinderi cemetery outside Kazan on Wednesday.
At its Muslim section, overgrown with weeds, Vladimir Nazarov laid to rest his 9-year-old grandson Ruslan who was on his way home from a sports camp with his mother, who survived. The woman was nowhere to be found at the boy's grave. Her relatives said a wave swept her out of the ship and her son couldn't make it, but she does not have a clear memory of the accident.
"Three minutes and he was dead. That's it," Nazarov told The Associated Press.
At the Christian section of the same cemetery, relatives were mourning the ship's captain Alexander Ostrovsky. He is reported to have stayed in the control room until the ship sank. His family believes he chose to sink with the vessel and blames the ship's owner.
"He fulfilled his civic duty till the end," Ostrovsky's former wife Tatyana told The Associated Press.
The captain's former colleague, Viktor Filatov, a tug boat captain, said that Ostrovsky was running a great risk by braving stormy weather on the Volga Sunday night, but put the blame on the ship's owner.
It's typical in Russia when ship owners "are simply forcing you to set sail for a trip" despite the weather conditions, Filatov said.
"They may know about (the ship's) malfunctions, but they are still trying to convince you to sail this way or another," he said.
Russia's Investigative Committee said Tuesday that the director of the tour agency that operated the Bulgaria and an official of the agency that registers river vessels had been detained and that a criminal case has been opened against them on charges that carry a sentence of up to 10 years in prison.
The committee opened a separate case against the captains of two ships that reportedly passed by at the time of the sinking but did not stop to offer help.
