Toxic gas which on Thursday leaked from tanks in a cargo warehouse in the Brazilian coastal city of Guaruja, close to Santos the country's largest and busiest port, has sent some 40 people to hospitals.
Guaruja fire department said rainwater apparently seeped into the container where the tanks containing sodium chloride isocyanate were stored, causing a chemical reaction that sent a large white cloud into the sky.
Guaruja Mayor Maria de Antonieta de Brito asked people to stay home because the gas can cause skin irritation, burning sensations, fainting spells and breathing problems.
The gas leak took place at a privately owned warehouse storage facility owned by logistics company Localfrio.
Localfrio spokeswoman Mariela Braga said emergency measures were in place and that the terminal had been evacuated. She added the gas that leaked was toxic, but not that toxic. But medical toxicologist Flavio Zambrone disagreed.
It is an extremely toxic product. It irritates the skin and eyes and if inhaled will also irritate the lungs he told the G1 news portal.
According to the Sao Paulo Port Authority, a fire that flared shortly after the leak began spread to 12 other containers carrying chemical products at the terminal. The fire was quickly put out, according to the fire departments.