Eleven miners were killed in a coal mine in central China on Thursday when their elevator failed, sending them plummeting to their deaths, state media said.

The workers were riding the elevator to the top of the mine in Henan province after finishing their midnight shift when the axis broke, plunging them 30 metres (98 feet) back down the shaft, Xinhua news agency said.

Citing local authorities, the agency said the accident occurred on Thursday morning during a shift change at the mine in Jiyuan city.

It said a screw on the elevator's axis broke.

China's coal mines are among the most dangerous in the world, with safety standards often ignored in the quest for profits and the drive to meet the huge demand for coal -- the source of about 70 percent of China's energy.

Nearly 3,800 lives were lost in Chinese coal mines last year, down 20 percent from the year before, according to official figures.

On Monday, state press reported 21 miners were killed in an accident at a mine in northern Shanxi province, one of China's prime coal producing areas.