The incident occurred about 4.00am local time Sunday in the north China province of Shanxi in Puxian County, representatives of the provincial work safety supervision bureau told Chinese news service Xinhua.
The total number of workers underground at the time of the blast is not known and rescue efforts are under way, the service said.
While there is obviously no official information on the number of illegal operations in the country, the Chinese government did announce in February it would close over 2,300 small collieries in the country by 2015 in an effort to increase safety and curb the increasing number of deaths in the country’s mining industry.
