The accident happened in Fengyuan coal mine in Hutubi County on Saturday evening, when staff were carryin out upgrading works at the site, the official Xinhua news agency said.
Eight of the 29 workers who were at the scene have been rescued from the mine, according to preliminary reports.
Rescuers have located the miners, with 12 on one platform, eight on a second platform, and the last worker in an escape route where water had entered, broadcaster CCTV reported.
“The working platform with 12 people is
1,200 metres (3,900 feet) from and the underground terrain is complex, making rescue difficult,” CCTV said.
Rescuers were also trying to pump water from the flooded shaft and have been piping air into the mine. Pumping equipment was being installed.
Mining accidents are common in China, where the industry has a poor safety record and regulations are often weakly enforced.
In January, 22 workers were trapped in a mine in east China’s Shandong province after an explosion damaged the entrance, leaving workers stuck underground for about two weeks.
Eleven men were pulled out alive, 10 died and one miner remained unaccounted for.
In December, 23 miners died after being trapped underground in the southwest city of Chongqing — just months after 16 others died from carbon monoxide poisoning at another coal mine in the city.