TOKYO, Oct. 5 (Kyodo) — High levels of radioactive cesium were found in an independent study in a Fukushima city district, prompting a citizens group and others involved to urge the government on Wednesday to promptly designate the area as one of the contamination hot spots for possible evacuation and ensure proper decontamination.

Up to 307,000 becquerels of cesium per kilogram of soil was detected in the Sept. 14 survey, triple that of the benchmark above which the government requires tainted mud to be sealed by concrete. The contamination is believed to have been caused by radiation leaked by the Fukushima Daiichi nuclear plant crippled in the March 11 earthquake and tsunami disaster.

The readings are comparable to the high levels in special regulated zones where evacuation was required after the 1986 Chernobyl accident, said the citizens group, Citizens Against Fukushima Aging Nuclear Power Plants.

It urged the government to designate the area as one of the hot spots, where residents are urged to evacuate, albeit not mandatory, due to accumulation of radiation in certain districts and would be eligible for state assistance if they decide to do so.

Kobe University professor Tomoya Yamauchi, who was in charge of the study that tested soil samples from five locations in and around the district, noted that decontamination conducted in some of the areas tested has not yet succeeded in reducing radiation back to the same levels prior to the March accident.

The Japanese government currently has designated two categories of evacuation zones -- the 20-kilometer no-go zone around the Fukushima Daiichi plant, and hot spots outside the zone where radiation level is expected to top 20 millisieverts a year.

The city of Fukushima is about 60 km from the crippled plant.

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