In Kashiwa, Chiba, where they measured 270,000 Bq/kg of Cesium in the ground,Ministry of the Environment measured 450,000 Bq/kg of cesium from 5~10 cm deep underground.
Measurement was conducted on 1, 2/11/2011, result was announced on 11/28/2011.
They assume radioactive material from Fukushima gathered in a gutter and then it leaked out from the broken part of the gutter into the ground.
(Source)