Eight coal miners were killed after a suspected gas explosion Tuesday in a mine in southern Poland, and fears were growing as rescuers tried to reach 15 others trapped more than 3,000 feet underground.

The accident occurred as the men were demolishing a wall in an underground corridor at the Halemba coal mine in the city of Ruda Slaska, said Southern Mining Co., which operates the mine.

“Eight are dead,” Jan Sienkiewicz, spokesman for the Halemba mine, said. He declined to give details.

The men were among a group of 31 miners who had been removing equipment from a shaft that had been closed for mining because it had been deemed too dangerous, said Prime Minister Jaroslaw Kaczynski, who flew to the mine and met with rescuers. He said eight miners had managed to escape.

Zbigniew Madej, a spokesman for Southern Mining Co., said rescue workers were digging their way through 500 yards of rubble in the hope of finding survivors. He added, however, that ventilation systems had been damaged in the shaft.

While the cause of Tuesday’s accident was not immediately clear, labor unions have complained that a lack of investment and massive layoffs in recent years have resulted in falling safety standards.