Russian authorities say the death toll from a cruise boat sinking on the Volga River has risen to 41, as rescuers continue their grim search Monday for more than 80 people who remain missing a day after the disaster.

Authorities say the vessel — more than a half century old — was carrying 208 people when it abruptly sank in bad weather Sunday, 750 kilometers east of Moscow in a huge river reservoir near the city of Kazan (in the republic of Tatarstan).

Russian President Dmitry Medvedev declared a national day of mourning for Tuesday, as he convened a special meeting of senior ministers Monday and announced a formal probe into the sinking. He referred to the doomed boat as one of a “number of old rust tubs we have sailing.”

Russian television showed hundreds of grieving onlookers, including scores of survivors, lining the shore near the disaster site. One man, who said he lost his entire family in the sinking, said two passing boats failed to render aid after the stricken cruise boat went down.

Survivors say the overloaded boat started listing to its side within moments of setting sail in heavy rains and high winds. They say it sank in about three minutes, giving the crew little time to take action.