At least 11 miners died in a coal mining accident in Russia's Siberia on Thursday and an operation to rescue dozens more people stuck underground was suspended due to the risk of an explosion, the region's governor said.
Coal dust caught fire in a ventilation shaft in the Listvyazhnaya mine in the snowbound Kemerovo region early on Thursday, filling the mine with smoke, the TASS news agency cited local emergency services as saying.
"The chance of an explosion is very high. We've decided to suspend the search and rescue operation until the concentration of gas reduces," Regional Governor Sergei Tsivilev said. Methane and CO2 levels were dangerously high, he said.
Eleven people were dead and 35 others were still underground, he said. Dozens were being treated in hospital, at least some of them with smoke poisoning. Four were in critical condition.
The coal industry region of Kemerovo roughly 3,500 km (2,175 miles) east of Moscow has been hit by fatal accidents for years.
The mine is part of SDS-Holding, owned by the privately held Siberian Business Union. The union had no immediate comment.
Before the rescue operation was halted, the governor said there was still electricity and ventilation in the mine, but that they had lost contact with some people deep underground.
"For now there is no heavy smoke, so we hope that there is no fire," Tsivilev said on his Telegram channel. "We have no communication lines with these people, the underground communications system is not working."
Some 285 people were inside the mine when smoke spread through the ventilation shaft, the emergency ministry said. At least 239 made it above ground, authorities said. They did not say what had caused the smoke.
On state television, President Vladimir Putin said he had spoken with the governor and emergency officials, describing the accident as a "great misfortune".
"Unfortunately the situation is not getting easier. And there's a danger to the lives of the rescuers... We'll hope they can save as many people as they can," he said.
The Kremlin said Putin had ordered the emergencies minister to fly to the region to help.
Kemerovo declared a three-day period of mourning.
In 2007, Kemerovo was the site of the worst mining accident since the 1991 collapse of the Soviet Union when an explosion at the Ulyanovskaya mine claimed the lives of more than 100 people.
In 2010, explosions at the region's Raspadskaya mine killed more than 90 people.
The Investigative Committee law enforcement agency's regional branch said it had opened a criminal case into negligence causing loss of life.