From a press release:
The Greensboro Fire Department, with assistance from the DH Griffin staff, has concluded its investigation into the fire that occurred last Friday. Based on details gathered from DH Griffin employees, moments before the fire was reported, a heavy machinery operator was suing an energized magnet to transfer powdered metals to the pile that became involved in the fire. During this process, a flash fire involving the powdered metal occurred, subsequently igniting other materials. It is believed that either static electricity or an electrical spark was the ignition source. Due to the magnitude of the fire and the resulting process of extinguishment, an exact ignition source cannot be determined.Previously.