===Response of Showa Denko===Showa Denko responded to the outbreak of Niigata Minamata disease in a similar way that Chisso had responded in Minamata: by attempting to discredit the researchers while proposing their own theory.
V marcu 1966 je bilo poročano, da je odpadna voda v obratu tovarne osumljena kot vir onesnaževanja, in v septembru istega leta je ministrstvo za zdravje objavilo, da je odkrito metilirano živo srebro v mahu na izhodu iz tovarne Showa Denko v naselju Kanose .