Five people are trapped in a flooded coal mine in Shanxi province, the official Xinhua news agency reported on Wednesday.

Rescue efforts are under way at the scene in Shuozhou city, in China’s coal mining hub, and the cause of the accident is under investigation, Xinhua said. The mine is owned by Huadian Power International Corp, a unit of major power generator Huadian Group.

The accident occurred at around 03:00 local time on Wednesday, when 91 miners were working at the mine, which has annual production capacity of 2.1 million tonnes. It wasn’t immediately clear whether operations at the mine were suspended due to the accident.

Calls to the mine went unanswered, while Huadian Power International declined to comment.

Reuters