SHIJIAZHUANG - China's coal mines have been ordered to conduct a safety overhaul to prevent major accidents as their frequency has surged in the past month.

Song Yuanming, deputy director of the the State Administration of Coal Mine Safety, said at the national coal trade fair held in Hebei Province that mines should not be operating over capacity and miners should not be asked to work overtime as mines pushed to the limits are prone to accidents.

He said there were on average two colliery accidents a month this year, but the rate peaked in November with five cases. In one serious case, 33 people were killed in a colliery gas explosion in Chongqing, southwest China.

Song also reiterated that no mines should operate without a license.