Sixty-four people missing after a massive pressure surge flooded part of a Russian dam are most likely dead, its owner said yesterday, indicating a likely death toll far higher than the 12 confirmed so far. "Finding anyone alive in the flood zone is unlikely, but the search continues," Vasily Zubakin, the chairman of state-controlled hydro-power company RusHydro, said through a spokesman.

A senior official at a local hospital near the Sayano-Shushenskaya hydroelectric plant said the death tally had officially risen to 12 from the 10 given on Monday night.

But 64 people were unaccounted for after a turbine room flooded early on Monday at the power station, Russia's largest. Emergencies Minister Sergei Shoigu confirmed this figure on Tuesday when he arrived on the scene.

Russia has been plagued for years by mine collapses, gas explosions and other catastrophes linked to creaking Soviet-era infrastructure.

After the global economic downturn gripped Russia last year, ambitious plans to revamp roads, ports and power stations were either scaled back or scrapped.

Mr Shoigu said that a sudden surge in water pressure had burst through one of the turbines and caused the flood. "The main reason for the accident was a hydraulic pressure surge, but the cause of that surge still needs to be investigated," he said.

Producing three times as much power as the Hoover Dam on the US Colorado River, the Sayano-Shushenskaya station was touted as a jewel of Soviet engineering when it was launched in 1978 on Siberia's Yenisei River.

But the turbines have not been overhauled since Soviet times, and the firm that built the destroyed turbine said yesterday that it was too old to work safely.