Twenty-one miners trapped in a coal mine in northwestern China have been confirmed dead, state news agency Xinhua reported Sunday.

A total of 87 people were working at the Lijiagou Coal Mine in Shaanxi province when an accident occurred on Saturday afternoon, Xinhua wrote. While 66 miners ascended to safety that day, 21 remained trapped. Local authorities said they are currently investigating the cause of the accident.

Operated by Baiji Mining Co. Ltd., Lijiagou had been approved for mining from July 2017 to July 2022, according to the Shaanxi Natural Resources Department. In March 2017, the Shaanxi Administration of Coal Mine Safety said the site was “producing and functioning normally.” Sixth Tone’s attempts to contact the provincial coal mine safety department, natural resources bureau, and emergency management bureau on Monday were unsuccessful.

While authorities have sought to ensure the safety of workers at the country’s coal mines — China is the world’s largest coal producer — accidents are still common. In October, 21 people died at a coal mine in the eastern province of Shandong after a rockfall trapped them in a 74-meter-long tunnel.

A total of 295 people died in coal mine accidents across China between January and November last year, a drop of 12.7 percent compared with 2017, according to the National Coal Mine Safety Administration. The figure has declined noticeably in recent times: In 2005, nearly 6,000 people were killed in accidents at coal production and mining sites.

Editor: Bibek Bhandari.

(Header image: Ambulances and rescue workers gather outside the Lijiagou Coal Mine in Shenmu, Shaanxi province, Jan. 13, 2019. Li Yibo/Xinhua)