2 miners are missing and 17 were injured after a coal mine accident in Poland

Two Polish coal miners remained unaccounted for and at least 17 were injured when a tremor struck the Rydultowy coal mine deep underground on Thursday, officials said. An earthquake was registered in that part of Poland at the time.

Seventy-six miners were brought to the surface, including 17 who were hospitalized immediately after the quake. One of them, with head injuries, was airlifted to a major hospital in the city of Katowice, officials said. Some of the injured were later discharged from the hospital.

Twenty specialized teams were taking part in the rescue operation in difficult conditions underground, authorities said.

Rescuers received signal from a location device of one of the unaccounted for miners and were trying to reach him, while searching also for the other one, said Damian Borgieł, a director at the Polish Coal Mining Groups, which operates the mine.

The cause of the tremor at about 1,200 meters (4,000 feet) below the surface and its immediate effects inside the mine were not immediately clear.

Spokeswoman for the mining group Aleksandra Wysocka-Siembiga said the accident took place at 8:16 a.m. The Euro-Mediterranean Seismological Center noted a magnitude 3.1 earthquake in southern Poland near the Rydultowy mine at that time.

Officials initially said that 68 miners were in the area at the time, but later raised that number to 78.

Łukasz Pach, head of the ambulance service in Katowice, the mining region's main city, said the hospitalized miners were in stable condition.

Mass rock tremors in coal mines resulting from stress building in the rock can lead to rock bursts, or sudden ejections of rocks into the corridors and tunnels that can be dangerous to miners in the area.

The Polish Coal Mining Group has suffered several deadly accidents this year.

In May, three miners died in a cave-in at the Myslowice-Wesola colliery, and one was killed at the same mine in April.

Two miners lost their lives in the Rydultowy mine in separate accidents in 2019 and 2020.

Opened in 1792, the Rydultowy mine currently employs about 2,000 miners.

Coal mining is considered hazardous in Poland, where some coal mines are prone to methane gas explosions or to cave-ins. Excavation in older mines goes deep into the ground in search for coal, increasing the job's hazards. The coal industry is among Poland's key employers, providing some 75,000 jobs.

Last year, 15 miners lost their lives in accidents.

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Associated Press writer Jan M. Olsen in Copenhagen contributed to this report.