At least 18 people have been confirmed dead following a carbon monoxide leak inside a coal mine in southwest China, the nation's Xinhua news agency reported on Saturday.

Those killed in the leak were among 24 people who got trapped in the mine around 5 p.m. local time on Friday when "excessive levels of carbon monoxide" began to seep into the air, according to the state news agency. One person has been pulled from the mine and rescue efforts remain underway to save five others still inside.

The accident occurred at the Diaoshuidong coal mine in the city of Chongqing. The mine had been suspended and shut down two months ago, and at the time of the accident workers were inside to dismantle equipment. Investigators were working to determine the cause of the accident, according to Xinhua.

The Diaoshuidong mine was built in 1975 and since 1998 has been operated as a private enterprise with an annual capacity of roughly 120,000 tons of coal. In 2013, three people died at the mine following a hydrogen sulfide poisoning incident, according to Reuters.

Friday's accident appeared an eerily similar replay to a September accident at the Songzao coal mine, which is also in Chongqing. At least 16 workers were killed after exposure to unsafe levels of carbon monoxide.

China, which is both the world's largest producer and consumer of coal, has now reported more than 100 coal mining accidents in 2020. In November, the government launched a year-long review of all working coal mines and coal-mining projects, focusing on infrastructure, risk prevention management and capabilities for emergency response and rescue.

The review was expected to put a brake on coal mining during a point in the year when production is often at its highest. Coal production in China typically ramps up between November and February in order to meet production targets. Through the first 10 months of this year, the country has produced 3.13 billion tons of coal. The U.S., by comparison, mined 706 million in all of 2019 — the lowest since 1978.

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