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The incident occurred early Sunday morning in southwest China's Yunnan province, local authorities told state news service Xinhua.
The accident happened around 4am when 12 miners were tunneling a mine shaft at the Bailongshan coal mine in the city of Qujing.
Three miners were lifted out of the shaft but rescue workers are continuing efforts to reduce gas levels in the mine so they can safely rescue the remaining eight.
The cause of the accident was being investigated, Xinhua said.
The coal mine is operated by the Diandong Energy under the China Huaneng Group, a major state-owned energy company.
