A flood in a south China coal mine has trapped 56 people underground, state-run media said Tuesday.

Rescuers have yet to make contact with the miners at the Nadu mine in Guangxi Zhuang Autonomous Region, Xinhua news agency said, citing the Guangxi Work Safety Administration.

It is not clear what caused the flood, which occurred Monday afternoon.

The State Administration of Coal Mine Safety director was heading to the location to oversee rescue efforts, Xinhua said.

China is the world's largest producer and consumer of coal, with demand rising alongside the boom in the nation's economy.

Nearly 3,800 lives were lost in Chinese coal mines last year, down 20 percent from the year before, the government reported in January, but independent labour groups suspect the actual death toll is much higher.