The fire occurred at a storage facility in the Brazilian coastal town of Guaruja, some 86 kilometers (54 miles) from Sao Paulo.
An area company, Localfrio, had been storing chemicals used to disinfect swimming pools at the facility.
Several explosions could be heard as flames from the blaze came into contact with the chemicals, releasing the noxious fumes.
A number of families have been ordered to temporarily evacuate the area, officials said.
Nearby residents were treated at local health centers for skin irritations, nausea and other complaints, according to officials, who said at this point that the fire is “almost extinguished.”