It happened at the Homalite Industrial plant on Brookside Drive where they make plastics.
Authorities say the blast happened just before 8:30 p.m.
Upon arrival fire crews reported smoke coming from the building and a partial collapse. Several other fire departments were called to assist.
Deputy Fire Marshals have determined that a chemical reaction caused the explosion and small fire.
The building was empty at the time of the explosion but it caused extensive damage estimated to be at several hundred thousand dollars.
The incident is still under investigation.