Initial investigation showed that substandard explosives had caused the coal mine blast that left 27miners dead and seven others trapped, Shanxi provincial coal mine safety watchdog said on Sunday.

"The substandard explosives stored in the shaft self-ignited, resulting in the deadly blast, according to an official with the provincial coal mine safety watchdog.

It said poor management on safety in production was another reason for the heavy casualties.

Investigations showed the mining company had exceeded its production quota, mined at unapproved working areas and was equipped with poor ventilation facilities, said Zhao Tiechui, the State Administration of Coal Mine Safety's director.

According to the safety rules, only 29 people were allowed to be working under the shaft at any given time, but 58 workers were under the mine when the accident happened, he said.

The explosion occurred at the Anxin Coal Mining Co. Ltd. in Xiaoyi City at about 11:00 AM on Friday. Fifteen managed to escape on their own and another nine were saved by rescuers. All the 24 miners were sent to nearby hospitals.

The bodies of 27 dead workers were pulled out of the shaft at about 5:00 PM on Saturday.

The search came to a halt at mid-day Saturday after rescuers found lots of unused explosives and detonators in the shaft and left the mine.

(Xinhua News Agency June 15, 2008)