BEIJING (AP) — An explosion at a steel mill in China's northeast killed 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, but experts believe an equipment malfunction was to blame, the announcement said.

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

The disaster occurred less than 12 hours after an explosion Wednesday evening blamed on cooking gas

killed 31 people in a barbecue restaurant