Gas exploded Tuesday in a coal mine in northwest China's Gansu province, killing about 20 miners, state media reported in the latest mining disaster to hit the country.

The official Xinhua news agency quoted Jingyuan Coal Industry Corp. general manager Wang Jun as saying 71 miners were working underground at the Weijiadi Coal mine at the time of the blast, and that 36 had escaped.

Of the 35 who remained inside, about 20 were killed, and the fate of the rest was unknown, Xinhua reported.

Wang said some injured miners had been brought to the surface but their exact number was not known, adding more than 30 rescuers were struggling to reach the trapped miners.

It was not known what triggered the explosion, Xinhua said.

A man from the security department at the Weijiadi mine confirmed some miners were found dead but he had no idea how many. He refused to give any more details.

China's poorly regulated mining industry is the deadliest in the world, with about 6,000 dying each year in explosions, floods, collapses and other disasters.

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