Twenty-three miners were trapped underground in a Chinese coal mine on Friday after a leak of carbon monoxide gas, state media reported.
Rescuers were dispatched to the Diaoshuidong mine in Chongqing, a huge metropolis around 1,800 west of Shanghai, and investigators were working to determine the cause of the accident, the Xinhua news agency wrote.
The report said the accident happened at around 5:00pm local time (0900 GMT) without giving further details.
An earlier accident at the mine claimed the lives of three people in 2013, Xinhua reported.
Mining accidents are common in China, where the industry has a poor safety record and regulations are often weakly enforced.
Sixteen workers were killed at another mine on the outskirts of Chongqing in September after a conveyor belt caught fire and the resulting blaze produced dangerous levels of carbon monoxide.
Two years ago, seven miners were killed in the city after the connecting segment of a skip broke and fell down a shaft.
In October 2018, 21 miners died in eastern Shandong province after pressure inside a mine caused rocks to fracture and break, blocking the tunnel and trapping the workers. Only one miner was rescued alive.