At least 198people had been confirmed dead Saturday in a fatal gas blowout which occurred Tuesday at a natural gas field of the China National Petroleum Corporation (CNPC)in southwest China,according to local government sources.

The gas field,in Kaixian County,is some 337kilometers northeast of Chongqing Municipality.The tragedy took place at 10:00p.m.Tuesday,when a well blowout suddenly and released a high concentration of natural gas and sulfurated hydrogen.

Chinese leaders including President Hu Jintao,Premier Wen Jiabao and Vice-Premier Huang Ju had instructed relevant departments to go all out in the rescue work.

The leaders called for effective efforts in evacuating local residents and making proper accommodation arrangements for them.

A work team headed by State Councilor Hua Jianmin arrived there Thursday evening to organize the rescue work.The cause of the accident is under investigation.

In another development,CNPC technicians inflamed the blowout gas to curb further gas spread Thursday afternoon as the CNPC and local authorities strived to contain the burst,a spokesman for the CNPC told Xinhua.

Some 260cubic meters of mud used for the containing of the blowout and 13special rescue vehicles were on the way to the scene,the spokesman said,adding that the mud would be pumped into the well Friday morning to stop the further spread of the toxic sulfurated hydrogen.

Operation of the gas field was normal before the gas suddenly blow out from the side of the drill,said Qian Zhijia,deputy headof the gas field.

Top municipal government officials have led teams from medical,civil affairs,public security and transportation departments.Residents within five square kilometers from the scene had been evacuated,said Wang Duanping,vice-governor of Kaixian county.