All 28 miners in the Xiaonangou coal mine in northwestern Shaanxi province died when an underground cable caught fire on Saturday night, Xinhua news agency said, citing the general office of the Shaanxi provincial government.
Police detained the owner of the mine.
Rescuers recovered some of the bodies, but Xinhua said they were hampered by an underground fire that was still raging on Sunday.
The mine, operated by the Xinxin Mining Co Ltd, was in the process of being extended so that output could be increased, according to the report.
In central Hunan province, officials were investigating the cause of an explosion at a coal mining area that killed two people.
Separately, in northwestern Gansu province, 13 miners remained trapped underground when a coal shaft flooded on Sunday. Three others were lifted to safety, Xinhua said.
Thousands of people are killed in China's mines every year despite government pledges to shut or consolidate many small or unsafe operations.
