Significant levels of airborne radiation have been detected in an area of Tokyo''s Setagaya Ward, exceeding readings in some evacuation zones around the crippled Fukushima Daiichi nuclear plant, prompting local officials to urge residents to stay away from the affected area. Radiation of up to 3.35 microsieverts per hour was recorded Thursday at a height of 1 meter along a sidewalk in a residential area of Tsurumaki in Setagaya, some 230 kilometers southwest of the Fukushima plant, Japan''s News Agency (Kyodo) reported. The ward is still investigating what type of radioactive material is involved, while trying to work out how to decontaminate the sidewalk, which is regularly used by pupils at a primary school. The area has been cordoned off as a precautionary measure.