The accident occurred when water from a nearby abandoned mine shaft flooded the Tiedingyan Coal Mine in Zheng'an County, local officials said.
Eight of 15 safety inspectors who were then underground checking for potential safety hazards during the raining season managed to escape.
Five were killed and two went missing. The rescue operation is under way, state-run Xinhua news agency reported.
The county has been lashed by heavy rains during the past few days, they added.