A fire at a coal mine in Russia‘s Siberia killed 11 people and injured more than 40 on Thursday, with dozens of others remaining trapped, authorities said.

Efforts to rescue those trapped in the mine were halted on Thursday afternoon because of an explosion threat, and rescuers were rushed out of the mine, administrators of the mine told the Interfax news agency.

The blaze broke out in the Kemerovo region in southwestern Siberia. Russia’s state Tass news agency reported, citing an unnamed emergency official, that coal dust caught fire, and smoke quickly filled the Listvyazhnaya mine through the ventilation system.

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A total of 285 people were in the mine at the time of the incident, Kemerovo Governor Sergei Tsivilyov said on his page on the messaging app Telegram. He said 35 miners remained trapped underground, and their exact location was unknown.

Tsivilyov said in another Telegram post that a total of 49 people with injuries have sought medical assistance. He had earlier reported a toll of 60 injured people and hasn’t offered any explanation for the revision.

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Earlier Thursday, Russia’s acting minister for emergency situations, Alexander Chupriyan, said 44 miners have been hospitalized with injuries. The difference in injury tolls reported by different officials couldn’t be immediately reconciled.

Russia’s Investigative Committee has launched a criminal probe into the fire on charges of violating safety regulations that led to deaths.

President Vladimir Putin extended his condolences to the families of the killed miners and ordered the government to offer all necessary assistance to those who were injured.

The Russian leader on Thursday afternoon sat down for talks with his Serbian counterpart Aleksandar Vucic in the Russian Black Sea resort of Sochi, during which Vucic also offered condolences to the families of the victims. Putin noted that the situation at the mine, “unfortunately, is not getting easier.”

“There is a danger to the life of the rescuers … Let’s hope that (they) will manage to save as many people as possible,” Putin said.

In 2016, 36 miners were killed in a series of methane explosions in a coal mine in Russia’s far north. In the wake of the incident, authorities analyzed the safety of the country’s 58 coal mines and declared 20 of them, or 34%, potentially unsafe.

The Listvyazhnaya mine in the Kemerovo region wasn’t among them at the time, according to media reports.

The latest inspection of the mine took place on Nov. 19, Interfax reported, citing officials from Rostekhnadzor, Russia’s state technology and ecology watchdog. The report didn’t offer any details on the results of the inspection.

According to Tass, the regional branch of Rostekhnadzor also inspected the mine in April and registered 139 different violations, including breaching fire safety regulations.