Many Japanese consumers seem dismayed to find out that there are people among them who would do such a thing, but there are people like that, unfortunately. And as the article cites one government agency, it is clearly none of the government's business to do anything about it anytime soon.
From Tokyo Shinbun paper version (not online; 10/3/2011), extremely quick translation subject to revision later if necessary:
Dilute cesium and sell - blend tea, garden soil - so that the cesium level is below the limit
After the Fukushima I Nuclear Power Plant accident spread radioactive materials, the provisional safety limit was set for variety of foods and goods. If an item tests less than the provisional limit it is considered "guaranteed safe". As the result, there are businesses that mix [radioactive goods] with those made in places far away from Fukushima Prefecture to dilute radioactive materials and sell them. Currently it is not against the law to do so, but the consumers who doubt the safety of the products and the producers who fear further "baseless rumor" damages are voicing concern.
FULL article ex-skf....