Bureau of sewerage in Tokyo published the measurement data of radiation contained in the incinerated ash of sewage sludge.
It is not the incineration ash of radioactive debris, but just normal sewage sludge.
The samples were taken from 3/6~3/13/2012. As the result, high level of cesium was measured from the incineration ash made at 12 of 12 sewage plants.
The highest reading was 12,100 Bq/Kg (Cesium 134 and 137) measured at Kasai Tokyo.