At least 13 people are dead and more than 100 remained missing after a Russian boat sank in the Volgar River on Sunday.

The ship could have been overloaded as the Associated Press reported that Emergencies Minister Sergei Shoigu was quoted by Russian news agencies on Monday saying that 208 people were believed to have been on board the Bulgaria when it sank Sunday afternoon. That figure is nearly 75 percent more than the 120 the boat was licensed to carry, officials said as reported by The Associated Press.

The Wall Street Journal reported that about 80 people were reported rescued, most by a passing ferry. The newspaper's article further states that investigators said the half-century-old Bulgaria sank in just a few minutes after being swamped by a large wave as the crew tried to maneuver in a sudden thunderstorm storm on the Kuibyshev Reservoir on the Volga.

The passengers and crew managed to get only a few inflatable rafts off before the ship sank, the Wall Street Journal article states.

The ship sank about three kilometers, or two miles, from shore in about 20 meters, or 65 feet, of water, officials told The Associated Press. Rescuers are still scouring the water of a Volgar River reservoir searching for survivors.

The Associated Press reported that many children were on board the boat, and that Russian news reports quoted survivors as saying about 50 children had gathered in the ship's entertainment hall shortly before the ship sank.