Inzai City is located in the northwest corner of Chiba where the radiation levels remain elevated.
From Asahi Shinbun (2/23/2012):
On February 23, the Japanese government ordered the governor of Chiba Prefecture to halt shipment of shiitake mushrooms grown in Inzai City in Chiba Prefecture. 993 becquerels/kg of radioactive cesium, exceeding the national provisional limit of 500 becquerels/kg, was detected on February 22.
The amount of radioactive cesium detected is nearly 10 times the amount of the new safety limit to be put into effect on April 1.
Still, many people don't seem to care, and the schools continue to use shiitake mushrooms, raw or dried, in their school lunches to feed small children.