The accident in the eastern Siberian region of Khakassia shut down the Sayano-Shushenskaya hydroelectric plant on the Yenisei River.

Casualty figures from Russian press sources varied, but the latest showed at least 12 dead, over a dozen injured, and up to 72 missing.

But emergencies ministry spokeswoman Irina Butenko told Reuters: "There is no danger to the population."

Explosion is not ruled out

She said authorities were not ruling out the possibility that an explosion caused the accident. But Russian news agencies reported a water surge was the most likely cause.

The Sayano-Shushenskaya plant provides power to nearby major aluminum smelters operated by RUSAL, Russia's largest aluminium producer.

Production was halted temporarily at some aluminium smelters, but a RUSAL spokeswoman said all their plants are now being supplied by other electricity producers and are working normally.

Water flooded the hall when a wall collapsed, after a sudden change in pressure caused the pipes feeding water to the hydro plant to burst.

No damage to dam

Local officials have said there is no danger to the dam.

"The body of the dam has not been damaged," said spokesman Dmitry Kydryavtsev. There was some panic among the local population and officials were reportedly trying to calm the situation.

The plant, which opened in 1978, is run by RusHydro and a spokesman said that repairs will take several weeks.

av/jen/Reuters/AFP/dpa
Editor: Trinity Hartman