KUNMING - A coal mine gas leak left at least 43 people trapped underground in the southwest province of Yunnan Thursday, local authorities said.

The accident occurred around 6:30 am at the Sizhuang Coal Mine in Shizong county in the city of Qujing, the Yunnan Provincial Emergency Response Office announced in a statement.

A rescue operation is underway, the statement said.

The Qujing municipal government said earlier a "gas explosion" had ripped through the mine.

The exact number of miners working underground at the time of accident occurrence is still under investigation.

Luo Lin, director of the State Administration of Work Safety, ordered local authorities to go all out to save the trapped miners.

Zhao Tiechui, deputy director of the State Administration of Work Safety, and Peng Jianxun, deputy director of the State Administration of Coal Mine Safety are en route to Qujing to oversee the rescue efforts.

The privately-run Sizhuang Coal Mine reports an annual output capacity of 90,000 tonnes.