UPDATE @ 12:50 p.m.:
The fire appears to be extinguished at Commonwealth Chemical in Fairfield, according to witnesses at the scene.
Witnesses reported seeing smoke from as far as two miles away when the fire broke out; however, there is no smoke visible now.
Oxidized materials that mixed with other chemicals are believe to have started the fire, according to Fairfield Deputy Fire Chief Randy McCreadie.
There was another incident at the business Nov. 27 when a forklift hit a pallet of chemicals, he said.
The hazmat units have not yet entered the building, but traffic is starting to be let through around the scene.
Multiple area fire and hazmat units are responding to a fire at Commonwealth Chemical in Fairfield.
Fire units were dispatched about 11:50 a.m. to 375 Distribution Circle. Police units are blocking off La Saint Court and Thunderbird Lane near the fire scene.
There is no information yet on injuries.
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We have a crew at the scene and will continue to bring you more information.