CAL FIRE/Fresno County firefighters were called to Custom Ag Formulators Incorporated on Willow Avenue near North Avenue.
Officials say the chemical spilled, and crews from the Fresno County Environmental Health Department, Fresno County Sheriff's Office and Fresno Fire were helping to mitigate the hazard.
CAL FIRE confirmed the substance that spilled inside the building was nitric acid.
All employees were evacuated from the building.
No one was injured, and investigators have not yet said what led to the spill.