Protestors at the gates of the Chisso factory: Minamata disease is caused by severe mercury poisoning. It was first discovered in Minamata city in Kumamoto prefecture in 1956. It was caused by the release of methylmercury in the industrial wastewater from the Chisso Corporation's chemical factory, which continued from 1932 to 1968. While deaths continued for 36 years, the government and company did little to prevent the pollution. In 2004, Chisso was ordered to clean up its contamination.