NEW : There is no immediate radiation threat , experts tell local officials . Local police cordons off an area in the Setagaya ward . The U.S. government issued a travel alert last week , warning Americans in Japan to avoid areas near the stricken reactors . Radiation there is higher than around Hiroshima . The damaged Fukushima nuclear plant could not be the source , experts say .
NEW : There is no immediate radiation threat , experts tell local officials . Local police cordons off an area in the Setagaya ward . Radiation there is higher than around Hiroshima . The damaged Fukushima nuclear plant could not be the source , experts say .