The incident took place in the early afternoon on Friday, May 17, at Milestone Inc., located at 25 Controls Drive in Shelton, said Shelton Police Det. Richard Bango.
According to Bango, the initial calls reported an explosion but after the fire department arrived it was determined that was not the case.
An investigation revealed a small hydrofluoric acid spill occurred and vapor from the chemical reached the ventilation system causing the building to be evacuated, he added.
There were no reported injuries.
Fire and hazmat crews are on scene and are expected to clear the building soon.
Click here to follow Daily Voice Newtown and receive free news updates.