Just days after the Fukushima Daiichi nuclear disaster began, in March, mysterious radioactive substances have been detected, and are still being detected, at sewage plants and incinerators around Japan.

The first case involves an incinerator in east Tokyo.  Ashes were found to be highly radioactive.  Unfortunately most of the ashes have already been recycled as building materials.  The radioactive isotope has not been identified.

Almost at the same time, sludge from sewage treatment plants in Tokyo also tested positive for radiation contamination.  Again, the isotope has not been identified.

Just this past week, in Maebashi, cesium contamination was found in incinerator ashes, sludge and molten slag, that were being processed at a water treatment plant.