Japanese waste incineration plants near Tokyo have found high levels of radiation in ash, and officials said Tuesday it may be from garden waste contaminated by the Fukushima nuclear disaster. The radioactive caesium was detected in plants in Kashiwa city in Chiba prefecture, northeast of Tokyo and about 200 kilometres (120 miles) from the plant that has leaked radiation since the March 11 quake and tsunami. Officials stressed that the radioactive ash collected in late June and early July, at concentrations of up to 70,800 becquerels per kilogramme, was safely contained within the plant and posed no health risk to the community. The level is far higher than the government\'s 8,000-becquerel per kilogramme limit, above which waste dumps must keep such ash in storage, and it presents authorities with the question of what to do with it. Authorities suspect the caesium may be from garden waste, such as tree branches and grass cuttings, that has been burnt in the facility. Kashiwa city official Kiyoshi Nakamura told AFP: \"Some people are believed to have cut plants and mown their lawns because of fear of radioactive contamination, and that waste was apparently brought to the plant.\" \"The radioactive ash is stored inside the plant, so the radiation has not been leaked into the environment,\" he said. However, another city official, Masaki Orihara, warned that \"we may run out of space to store the ash in about 55 days. There may be no other way but to end up suspending incinerators in the worst case.\"