"Two acids were put into a waste container. Typically they are compatible, but the waste container had some other substance in it," Mansfield said.
Mansfield said the employee likely was unaware the other substance was in the waste container, resulting in the unexpected chemical reaction on Monday.
Mansfield said a call came in around 4:25 p.m. for a general fire alarm, but was then upgraded to some sort of "event.''
When firefighters arrived at the Morpho Detection building, 23 Frontage Road, in an industrial park, they found a "green vapor cloud" hovering above the building, officials said.
About 100 people were evacuated from the building, and no injuries were reported. The cloud dissipated quickly, and Mansfield said officials determined it posed no danger to the public.
"There was no general public evacuation," he said.
He said the Hazmat team determined there was a small explosion inside the building.
"One employee described it as a tractor-trailer hitting the building," Mansfield said. The Hazmat team cleared the building around 10:15 p.m. Monday and a cleanup team arrived shortly thereafter.
"We had a unit there assisting. Our last unit left around 3 a.m. this morning," Mansfield said Tuesday.
The Occupational Safety and Health Administration is assisting in the investigation.
Morpho Detection is a security company that develops explosive and drug detection systems for places like airports.
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