The criminals included local officials and employees at a state company, according to reports.
The pipeline, owned by a subsidiary of China’s largest oil refiner Sinopec, exploded as a result of drilling by maintenance staff.
A court in the eastern city of Qingdao, where the accident occurred, meted out sentences of three to five years to the defendants, the Xinhua state news service reported.
An official inquiry into the blast in 2014 identified negligence as the primary cause of the explosion, taking Sinopec and the city’s government to task for “not identifying and correcting potential safety hazards”.
The blast highlights the risks involved as both energy pipeline networks and China’s cities expand rapidly. Urban development has engulfed many existing pipelines, providing an opportunity for thieves but also leaving lines dangerously close to residents, industry and commerce.