A Union Carbide pesticide plant located in the heart of Bhopal, India released 40 tonnes of methyl isocyanate gas. This gas is heavier than air, so it drifted along the ground throughout the city. Approximately 3,000 died immediately from the gas. It caused pulmonary edema in most of the victims. Later, thousands more died, days after exposure. Some victims died from being trampled as they tried to escape the city. Over a hundred thousand people were left chronically ill.