The Environment Ministry said Monday that no evidence has been found to prove the link between contaminated water in a well in Kamisu, Ibaraki Prefecture, and chemical weapons buried in the area by the Imperial Japanese Navy after World War II.
The ministry completed its examination Friday.
Prefectural officials believe the water, which contains high levels of arsenic, was contaminated by poison gas chemicals abandoned by the Imperial navy after World War II. The navy had a chemical laboratory in the area.
"We will analyze the data and present the analysis to the residents" of Kamisu before deciding whether to conduct any further investigations, Vice Environment Minister Shigeru Sumitani said.
The ministry used radar and conducted drilling surveys at 25 sites around the well between May 29 and July 4 in its fruitless search for buried containers of arsenic.
In June, the government said it would shoulder the medical bills of locals who fell ill after drinking water from the well, a rare step given that no clear link had been established between their health problems and state responsibility.
The ministry decided to pay residents' medical bills because "it is highly likely that the well was contaminated by poison gas abandoned by the Japanese military," Environment Minister Shunichi Suzuki said at the time the decision was announced.
A total of 98 people began applying for the assistance on July 1. After submitting urine and hair samples, 30 were deemed eligible for state aid as of Friday.
In March, the Ibaraki Prefectural Government found that water in the well contained arsenic levels 450 times the national standard.
The test was conducted after residents began complaining of health problems after consuming the water.