BEIJING—An explosion at a steel mill in China’s northeast killed at least four people and left five hospitalized with injuries, the city government said Friday.

A blast furnace exploded Thursday morning at the Yingkou Iron and Steel Co., Ltd. in Yingkou, east of Beijing in Liaoning Province, the city’s Emergency Management Bureau said in a statement.

The cause was under investigation.

Phone calls to the Yingkou government Friday weren’t answered.

The actual number of casualties from such events may be much higher. The actual number of casualties is difficult to verify, as the Chinese regime routinely suppresses or alters information.

The disaster occurred less than 12 hours after an explosion Wednesday evening blamed on cooking gas killed at least 31 people in a barbecue restaurant in Yinchuan, a city in China’s northwest.