Investigators put have attributed the blast on the negligence of the drilling crew, who dismantled the equipment which would have contained the gas. The subsequent release of natural gas and hydrogen sulphide also harmed 9,000 people and forced the evacuation of 41,000 villagers in a 10 sq km area.

The six are Wu Bin, Wang Jiandong, Song Tao, Wu Hua, Xiang Yiming and Xiao Xiansu. It is unclear whether the six will appeal their sentences.

The leader of the drilling team, Wu Bin, has been sentenced to six years for failing to report the inherent danger and not taking necessary measures to correct the danger. Engineer and on-the-spot team leader Wang was sentenced to five years for demanding well workers remove the safety back-pressure valve, as was well regulator Song for failing to stop Wang’s decision.

Wu Hua, the former deputy manager and chief engineer of the Eastern Sichuan Drilling Co and the director of the company’s emergency centre, was sentenced to four years for failing to assign special personnel to monitor the blowout and failing to take the necessary actions following the blow-out.

Driller Xiang was sentenced to three years for failing to follow proper drilling procedures, as was Xiao, the well recorder, for failing to report work violations to her superiors. Xiao, however, has received a reprieve of four years.