Four miners were dead and another two were still missing as of Wednesday noon following a coal mine gas outburst in central China's Hunan Province, local authorities said.

Six miners were believed to be trapped underground after the accident occurred Tuesday morning in Shimen Coal Mine in Longhui County, Hunan, according to the county committee of the Communist Party of China (CPC).

Rescuers have discovered the bodies of four miners and were still searching for two others.

"We will not stop searching until we find all the trapped miners," said Zhong Yifan, Party secretary of Longhui.

Zhong vowed to investigate the cause of the accident and to launch a campaign in the county to strengthen safety in coal mine production.

Shimen Coal Mine produces around 60,000 tonnes of coal annually and was undergoing an expansion project before the accident.