The incident took place yesterday at the Xiangshui Mine in Guizhou province, state-run Xinhua news agency said.
Five people were rescued and efforts were under way to rescue those who remain trapped, it said.
"The search is full in swing after gas density in the pit has declined, and rescuers are expected to reach the trapped miners this afternoon," said Yin Zhihua, vice mayor of Liupanshui.
Twenty-eight miners were working underground when the accident occurred.
China has the world's deadliest coal mine industry. In August, a mine blast in southwestern China's Sichuan province killed 44 people. PTI
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