Agano River
In the spring of 1966, the research team determined the most likely cause to the dumping of methylmercury from Showa Denko Corporation factory. Showa Denko was located upstream on the Agano River and, just like the Chisso corporation, produced methylmercury as a by-product and then dumped it into the Agano river. Much like Chisso corporation, Showa Denko declined all charges that they were at fault for the Niigata Minamata outbreak.