Carbon monoxide poisoning killed 23 miners who became trapped in a coal mine in southwest China on Friday. One survivor was rescued from the Diaoshuidong mine in Yongchuan district in Chongqing. Chinese media reported that the mine had been due to close two months ago after its permit expired and the owner had been selling equipment as scrap metal. The 24 miners who were trapped had been sent down to help dismantle the equipment, Southern People Weekly reported, two weeks after a group of miners had confronted the owner about unpaid wages. State news agency Xinhua reported that the local emergency command headquarters suspected the removal of the equipment contributed to the build-up of the deadly gas. Canada extends review of Chinese state firm’s Arctic gold mine bid There were no further details about the possible cause of the accident, but the State Council, the country’s cabinet, is supervising an investigation. Media reports said that an odourless white smoke was spotted coming out of the depths of the mine at around 5pm on Friday, and monitoring equipment showed that carbon monoxide levels were far above the safe limit. The highest concentration of carbon monoxide was recorded at 1,700 parts per million, 34 times the amount an adult can withstand, according to Southern People Weekly . The rescue operation finished on Saturday night, with 18 of the 23 bodies of the dead miners recovered from the pit. The Diaoshuidong coal mine once produced 120,000 tonnes of coal a year and employed hundreds of people, local media reported, but the workforce has shrunk in recent years to around 100. It was the second deadly gas leak at the mine in recent years, according to Xinhua. In 2013 three miners were killed and two injured by a hydrogen sulphide leak. In September this year, another deadly accident happened at a mine in Chongqing , when carbon monoxide killed 16 and poisoned 38 others after a conveyor belt caught fire at the Songzao mine on the outskirts of Chongqing. In 2016, a gas explosion at the Jinshangou coal mine in Yongchuan district, killed 33 miners trapped underground. China is the world’s largest producer and consumer of coal and its mines are among the world’s deadliest. According to the National Coal Mine Safety Administration, in the first half of 2020, there were 56 accidents and 81 deaths nationwide. Should Chinese miners’ bones in shipwreck be raised for burial? Inadequate safety regulations, poor equipment, lack of supervision, and local government corruption are considered to be the main reasons for the high number of accidents. On Sunday, state broadcaster CCTV reported that the State Council safety commission office had warned the Chongqing municipal government over its safety record. It said officials had been told to examine the causes of the two recent fatal accidents and improve safety measures. They were told the accidents highlighted weaknesses in safety checks and supervision and warned that some mining enterprises needed to improve their accident awareness.