According to Xinhua the accident happened at the Sizhuang coal mine in Shizong county around 6.30am.
It is believed that the gas leak occurred at one platform inside the shaft and later spread to another platform inside the mine.
Initially the government had blamed the deaths on a “gas explosion” at the mine following a preliminary investigation.
Xinhua said a rescue operation was underway, involving a team of firemen and rescue experts in an effort to save the remaining 23 people underground.
However, the number of people trapped could change as the exact number of people working underground at the time of the accident is still being investigated.
According to China Daily, the Sizhuang private coal mine was operating without a mine license which had been revoked a year ago.
The accident comes just a week after eight Chinese miners were killed at the Qianqiu coal mine after a rock burst tore through the mine.
China’s coal mines remain the most dangerous in the world, despite a recent government crackdown on illegal and unsafe mines.
According to figures obtained from the State Administration of Coal Mine Safety, 2433 miners were killed in coal mine accidents in China in 2010.