Savechild.net has the information posted on the Ministry of Health, Labor and Welfare website. The ministry has been conducting the sampling tests on food items currently sold in the marketplace, while the Ministry of Agriculture, Forestry and Fisheries do the sampling tests on produce before they are sold in the market.
According to the table below from the Ministry of Health, the yogurt was sold in Niigata Prefecture, and tested by the lab in Niigata Prefecture. The yogurt contained 3.4 becquerels/kg of cesium-134, and 3.1 becquerels/kg of cesium-137. It was made in Kami-machi in Miyagi Prefecture, about 135 km from Fukushima I Nuke Plant. But the distance doesn't mean much, as the raw milk used to make yogurt could have come from anywhere and everywhere. (They do mix and match.)
