State and local government officials say they have detected radioactive substances exceeding government safety limits in soil at the bottom of agricultural dams and reservoirs in Fukushima Prefecture.
The agriculture ministry and the Fukushima prefectural government found 8,000 becquerels or more per kilogram of radioactive substances in 568 out of the 1,940 dams and reservoirs they inspected between last June and December.
108 were in the evacuation zones around the Fukushima Daiichi power plant, and 460 were further away.
Officials detected 370,000 becquerels per kilogram in the soil of a reservoir 58 kilometers away from the plant.
It is the highest reading so far recorded outside the evacuation zones, and more than 46 times the government limit of 8,000 becquerels for radioactive waste.
The state government is obliged to dispose of radioactive waste beyond this limit.
Prefectural officials say rain may have carried radioactive substances into the waters from surrounding forests.
Water from the reservoir with the highest reading outside the evacuation zones is being used for rice paddies nearby. But officials say they have not found radiation levels exceeding food safety limits in locally-produced rice, probably because radioactive substances in the soil barely dissolve in water.
The head of an association of residents says officials have told them they will not be exposed to radiation as long as there is water in the reservoir.
But he says they fear radioactive levels may surge if it dries up. He is urging the state government to address the problem as soon as possible.