An explosion at a coal mine in central China killed 26 miners who were working despite an order to halt production, officials said on Wednesday, while a mine tunnel collapse elsewhere left four dead in the latest accidents to strike the country’s mining industry.

The death toll from the blast on Tuesday evening at the mine in Henan province’s Mianchi County doubled after 13 more bodies were found, said an official surnamed Li from the Henan Administration of Coal Safety.

Another 20 miners managed to escape from the mine, he said, adding it was unclear why the mine had initially reported that only 33 miners were working underground at the time of the blast.

A police investigation is under way, the official Xinhua News Agency reported. Most such accidents are usually blamed on a buildup of coal gas or methane ignited by sparks or open flames.

The mine belonged to the Juyuan Coal Industry Co., a subsidiary of the state-owned Yi Ma Coal Industry Group, and had been ordered to halt extractions while its operations were reorganized, Xinhua said. It was unclear why the mine was still in operation.

With an annual production of 150,000 tons of coal, the mine is typical of the mid-size operations that China has been seeking to consolidate into safer, more efficient operations.

In a separate accident on Tuesday, a coal mine tunnel in northeastern Liaoning province collapsed, leaving four miners dead, Xinhua said, citing local authorities. Three other men managed to escape from the shaft owned by the Caitun Coal Mine in Benxi City.

The state-controlled coal mine was under renovation when the accident happened. The provincial coal mine safety department set up a working group to investigate the accident.

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