At the Listvyazhnaya mine in the Russian town of Bilovo, Kemerovo Region, a gas leak on Thursday killed at least 52 people, including six rescuers who were sent to try to rescue dozens of people in one of Russia's most serious disasters for more than. Reported by AP.

The Regional Investigative Committee reported that three people, including the director of the Listvyazhnaya mine and his deputy, were detained on suspicion of violating industrial safety rules.

It said that the miners suffocated when the ventilation shaft filled with gas.. State television reported methane explosion, according to prosecutors.

Among the dead - 11 miners, the dead have already been confirmed, 35 missing and six rescuers.

Dozens of people have been hospitalized, at least some of them due to smoke poisoning. Four were in critical condition.

According to the Ministry of Emergency Situations, about 285 people were inside the mine when smoke spread through the ventilation shaft.. Authorities said 239 people made it to the surface.

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After purchase by Akhmetov, a large mine became unprofitable.

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Three days of mourning declared in Kemerovo.

The coal mining region of Kemerovo, about 3,500 km (2,200 mi) east of Moscow, has had fatal accidents over the years.

Listvyazhnaya mine is part of SDS-Holding, owned by the private Siberian Business Union. The owner did not comment..

In 2007, the region suffered the worst mine accident since the collapse of the Soviet Union, when an explosion at the Ulyanovskaya mine killed more than 100 people.. In 2010, explosions at the Raspadskaya mine killed more than 90 people.