The company used unconventional methods to get rid of methane, the report said. Some workers even rigged their machines to bypass the methane sensors after the machines kept automatically shutting down — something they were designed to do when methane levels got too high.
The company made a "major error" by placing a ventilation fan underground instead of on the surface, the report found. The fan failed after the first of several explosions, effectively shutting down the entire ventilation system. The company was also using water jets to cut the coal face, a highly specialized technique than can release large amounts of methane.
The report did not definitively conclude what sparked the explosion itself, although it noted that a pump was switched on immediately before the explosion, raising the possibility it was triggered by an electrical arc.
The now-bankrupt Pike River Coal company is not defending itself against charges it committed nine labor violations related to the disaster. Former chief executive Peter Whittall has pleaded not guilty to 12 violations and his lawyers say he is being scapegoated.
An Australian contractor was fined last month for three safety violations after its methane detector was found to be faulty at the time of the explosion.