St Paul (Learfield News Service) - The Minnesota State Fire Marshal Division says a compressed natural gas leak led to the January explosion at McNeilus Truck and Manufacturing in Dodge Center.

Four workers were seriously hurt in the explosion at the plant on January 11th. An additional two employees were treated for minor injuries at the scene. An investigation led by by Deputy State Fire Marshal Steven Wolf revealed that the compressed natural gas (CNG) system on top of a refuse truck leaked four cylinders of natural gas into a baking room. Wolf said due to the downdraft air exchange system, the air was removed and re-circulated quickly and reached an explosive limit, which was ignited by an unknown source. Wolf said a loose hose on the CNG system led to the leak, but what made the hose come loose in the first place remains unknown.

Wolf said that he has closed the investigation, but may reopen it should he receive any new information.

The Occupational Safety and Health Administration has found a serious violation was involved in the explosion and is seeking a $7,000 penalty in the case.

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