As many as 55 people were working in the mining shaft when a gas leak took place at the Jilinqiao colliery in Huangfengqiao Township, Youxian County yesterday.
The rescuers brought the remaining 37 miners to safety and rushed them to hospital, state-run Xinhua news agency reported.
Investigators are still testing substances in the poisonous gas. Police have detained those responsible for accident pending investigation
China, which is the world's largest coal producer, witnesses frequent deadly accidents in mines.
In March, seventeen coal miners were killed when a lift used to move workers fell down a shaft in northeastern Heilongjiang province.
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