The Environment Ministry on Monday will dispatch eight officials to Kamisu, Ibaraki Prefecture, to investigate a well that has been found to contain high levels of arsenic.
The Imperial Japanese Navy had a chemical lab in the town during World War II, and prefectural officials said they suspect the well water has been contaminated by stores of poison gas.
A total of 18 people have complained of feeling ill after drinking water from the well, according to the prefecture.
The central government will set up a new investigation team next week to deal with the case, responding to demands made Wednesday by Ibaraki Gov. Masaru Hashimoto. The team will include officials of the Environment Ministry, the Defense Agency and the Health, Labor and Welfare Ministry.
The team will also investigate an incident in which bottles containing poison gas chemicals were found at a construction site in Samukawa, Kanagawa Prefecture, in September. They are believed to have been abandoned by the Imperial Japanese Army after World War II.