Firefighters from across the San Gabriel Valley and Los Angeles County responded to a HazMat situation early on December 9, 2013, which required the evacuation of nearly 200 employees from nearby industrial companies.
Monrovia fire officials told the San Gabriel Valley Tribune that a three unknown chemicals had been mixed together to create a cocktail of hazardous gas.
The chemicals have since been identified as cyclo aliphathic resin, boron trifluoride, and ancamine.
At least 50 of the evacuated employees complained of headaches and nausea from the fumes. Some were taken to hospital.
The fumes, carried through a ventilation system, originated at Air Logistics Corp, which mixes chemicals as part of its manufacturing processes in Southern California.