The Tokyo Metropolitan Government said Tuesday that it had found arsenic levels 2.4 times above the legal limit in soil at the Tsukiji fish market site in 2013.
It was the first time contaminants were detected in the Tsukiji soil but the metropolitan government said there was no risk to public health as the site had since been paved over.
The arsenic was detected during a soil pollution probe that was conducted between May and June 2013 to check whether excavated soil from road construction taking place south of the market was meeting environmental quality standards.
Other than arsenic, levels of fluoride 1.6 times above the safety standard were also detected.
The metro government reportedly said it did not disclose the findings because there had been other cases where contaminants were detected in soil during construction work that remain undisclosed.
The metro government plans to conduct another soil investigation at the Tsukiji site soon, though the results are not expected for several months.
Last year, the metropolitan government compiled a separate report that said the Tsukiji fish market site may be contaminated by chemicals used in a postwar dry-cleaning plant.