Four people were killed and three injured in an explosion, which police are treating as suspicious, at a mine in north China's Shanxi Province, police said on Wednesday.

The explosion occurred at about 4:00?PM on Wednesday in the offices of the Shanjipo coal mine in Taitou town, Xiangning county, when the mine manager was playing mahjong with several other people, said a Xiangning police officer.

The injured people have been taken to hospital. The identities of the dead are still unknown.

The officer said local police have listed it as a criminal case and are investigating, without giving details.

(Xinhua News Agengy August 16, 2007)