Three workers have died following a poisoning accident at a copper mine in Yuanqu county, Yuncheng, Shanxi province, on Tuesday.

The accident occurred on Tuesday at the Luojiahe Copper Mine and was caused by gunpowder smoke, according to a statement from the National Mine Safety Administration on Wednesday.

It said blasting operations underground can generate large volumes of poisonous gas, and if the shaft space is narrow, ventilation is poor, or regulations are not followed, the risk of poisoning increases significantly.

Authorities have urged mines across the country to draw lessons from the incident, reinforce safety protocols, ensure strict compliance, and prevent similar accidents.

An investigation into the case is underway.