Beijing, Nov 11 (IANS): A day after 43 miners were trapped underground following a gas leak in a coal mine in southwest China's Yunnan Province, hundreds of rescuers were still searching for the 22 who are still alive inside, Xinhua reported Friday.

At least 21 of the trapped miners perished in the tragic accident Thursday morning.

Ventilation machines were pumping excess methane gas out of the mine, while rescuers were taking turns braving high levels of gas, coal dust and debris in the pit to find survivors in the Sizhuang Coal Mine, located near the industrial city of Qujing.

"We must rescue the trapped miners at all costs," said Zhao Tiechui, deputy director of the State Administration of Work Safety, at the site early Friday.

Coal dust forced out of the mine shaft by expanding gas has blanketed the area around the shaft's entrance.

The private mine was operating without a licence when the accident occurred. The mine's licence was revoked a year ago, said local work safety official.

"It is an accident that should not have happened. It exposes a lack of supervision by the local government. We must learn a lesson from this accident," Zhao said.

A preliminary investigation showed that the gas leak occurred at one platform inside the mine shaft but later spread to another platform, trapping a total of 43 miners on the two platforms at about 6.30 a.m. Thursday.