Twenty miners have been confirmed dead after a coal mine gas leak accident in the southwestern province of Yunnan Thursday, and hundreds of rescuers are rushing to save the 23 people still trapped underground, local authorities said.

A coal mine gas leak left at least 43 people trapped underground in southwest China's Yunnan Province on Nov.10, local authorities said.[Photo/YNTV.cn]

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

A preliminary investigation showed that the gas leak occurred at one platform inside the shaft but gas later spread to another platform, trapping a total of 43 miners working on the two platforms.

A rescue operation involving about 30 firefighters, 100 professional rescuers and 300 medical workers is underway, the statement said.

Meanwhile, more than 30 ambulances were also on site, it said.

Instead of "gas leak," the Qujing municipal government said earlier that a "gas explosion" had ripped through the mine.

Luo Lin, director of the State Administration of Work Safety, ordered local authorities to put forth all efforts 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 rescue efforts.

The mining industry has been a pillar of Shizong's economy, making up 65 percent of the county's industrial output and contributing 54 percent to its GDP last year.

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