The Russian president has ordered the creation of a state commission to investigate the deadly weekend sinking of a tourist ship on the Volga River.
Dmitry Medvedev's order came a day after 47 people, including three children, died and scores more were reported missing and presumed dead after the Bulgaria sank in a wide stretch of the river in the Tatarstan region.
Medvedev declared Tuesday a national day of mourning. The investigatory commission will be led by the transport minister, he said.
Eighty survivors were pulled out of the water by a passing craft on Sunday, but Sergey Shoygu, the Russian emergency situations minister, said there was almost no hope of finding anyone else alive.
The Bulgaria was officially carrying 183 passengers, but Shoygu said the double-decker ship was overloaded with at least 25 unregistered people.
The prosecutor assigned to Volga River issues said the ship was running with a "defunct" left engine and had pumped fuel to the right side, where "technical water" also was being stored, causing the Bulgaria to tilt, the Russian Interfax news agency reported.
He also said the carrier operating the Bulgaria was not licensed to conduct tours.
The boat was heading to the regional capital, Kazan, about 830km east of Moscow, when it sank in water about 20 metres deep at around 2pm local time (11:00GMT), the emergency situations ministry's regional branch said.
Al Jazeera's Neave Barker, reporting from Moscow, said that since the river was very wide and the ship was in a remote section of the waterway, it was unlikely that help arrived quickly.
The ship was originally reported to have carried 125 passengers, 22 crew and 35 other staff.
River 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.
Accidents rarely lead to major fatalities. The last shipping accident recorded by Russian state media occurred in September 2010, when seven people were killed on a lake above the Arctic Circle.
It was unclear whether the Bulgaria, which state TV said had dozens of cabins and two restaurants, was on a one-day outing or a longer cruise.
Source: Al Jazeera and agencies