Four employees of the subsidiary, Hulun Buir Chihong in Inner Mongolia, inhaled a toxic gas preliminary findings indicate was carbon monoxide during an inspection of equipment on Monday evening, Chihong said in a filing to the Shanghai Stock Exchange.
Three died at the scene, and a fourth is being treated in hospital but is not in a life-threatening condition, it said.
Hulun Buir Chihong had planned to produce 131,600 tonnes of zinc ingots in 2021 and churned out 60,700 tonnes in the first half, Chihong said.
Production and operation at the subsidiary had been suspended on the orders of the local emergency management bureau, the company said.
The cause of the accident, duration of production halt, and impact on the company are pending further investigation, according to the filing.
Chihong said it would actively cooperate with the investigation into the incident and strengthen efforts to deal with potential safety hazards.
Industrial accidents are common in China. A suspected gas leak at a Sichuan food company https://weibo.com/2656274875/Kh4AtuU4y?type=comment#_rnd1629252471599 in May killed seven. In July, one death was reported from a liquid ammonia leak in a unit of Yunnan Yuntianhua.
Zinc prices on the Shanghai Futures Exchange closed at 22,675 yuan ($3,497.77) per tonne on Tuesday and were trading range-bound on Wednesday.
($1 = 6.4827 yuan)
(Reporting by Tom Daly and Min Zhang; Editing by Karishma Singh)