Nine coal mine managers were sentenced to between two and six years in jail for a coal mine blast that killed 108 miners and injured 29 others in north China's Hebei Province, Xinhua quoted a local court as saying today. Shang Zhiguo, head of the Liuguantun colliery, was sentenced to six years in jail for committing a major workplace safety crime. The deputy head Li Qixin, who was also in charge of production safety, was jailed for five years on the same charge, according to Kaiping District People's Court ruling on Tuesday afternoon. The coal mine investor Zhu Wenyou and head of the mine safeguard department Lv Xuezeng were jailed for three years each. The mine ventilation department chief Liu Wencheng was jailed for fours years. Another four managers were sentenced to between two and four years in jail. No defendants appealed the judgment. The gas explosion happened at the Liuguantun Coal Mine in Kaiping District of Tangshan City at 3:30 p.m. on Dec. 7, 2005. The gas blast was a serious accident caused by the illegal operation of the mine, Li Yizhong, former director of the State Administration of Work Safety, had said. The coal mine was still under construction and did not have a production license before the accident happened, said Li. An investigation revealed that the original design of the coal mine had been changed without approval. The altered designed, which neglected safety considerations, allowed the exploitation from eight directions for a single coal layer without proper ventilation or gas surveillance systems. The coal mine, formerly state-owned and with a designed annual production capacity of 300,000 tons, was privatized in 2002.