China's deadliest coal mine explosion in years was caused when the miners dug too deep and poor ventilation allowed gas to build up to dangerous levels, the official Xinhua news agency said on Sunday. The gas was ignited by sparks from a running engine, it said, citing the results of an investigation into the accident that killed 148 miners at Daping mine in the central Chinese province of Henan on Oct. 20. "The mine operators failed to realize that the further extension of the mine would greatly increase amount of gas in the tunnel," Xinhua said citing Zhao Tiechui, deputy head of the State Administration of Production Safety. "The inefficient ventilation increased the density of gas," it said, citing the results of the investigation. Nearly 450 miners were underground at the time of the explosion, which injured 32. Fifteen of the injured had been discharged from hospital and the rest were in stable condition, Xinhua said. The accident was the worst in several years for China's notoriously accident-prone coal mining industry, the primary source of fuel for the world's seventh-biggest economy. Mines have expanded with little regulation to keep up with booming demand, with deadly consequences. In the first nine months of this year 4,153 miners died in accidents.
