The owner of a catamaran which crashed into a barge in the Volga river near World Cup host city Volgograd, killing 11 people, was "in a state of intoxication", investigators have said.
The Investigative Committee of Russia said the sightseeing boat was also not registered and was over capacity when it crashed on Monday.
Rescue services managed to save five of those on board, with three taken to hospital, according to a statement on the regional government's website.
England fans are set to descend on Volgograd for the Three Lions' first match against Tunisia on Monday.
River cruises along the Volga are a popular tourist activity.
But fans may be concerned after investigators said preliminary findings suggested the owner of the catamaran which crashed had ignored light and sound warnings from the cargo ship, allowed 16 passengers to board when the boat had a capacity of 12, and six life jackets were found unused.
The owner of the boat station is being sought by authorities for allowing it to operate on the river, the Investigative Committee statement added.