State Police have determined that an employee at National Plastics improperly discarded a piece of burnt plastic July 15 that led to the massive fire at the Palmer Township facility, The Express Times reports.

The employee had conducted a “burn test” on a piece of scrap and then tossed it in with other debris. The resulting fire took firefighters from 25 departments in four counties more than six hours to completely put out.

Initial reports stated the fire at the plastics recycling company started in a dumpster at about 11am and then jumped to the building at 11 McFadden Road. At times, the smoke billowed so high that it could be spotted for miles around the Lehigh Valley. 

National Plastics, according to its website, "is a post-industrial plastics recycling company."