NEW YORK (Kyodo) -- A senior official of the U.S. nuclear regulatory agency said Thursday he had believed there was a "strong likelihood" of serious core damage and core melt in reactors at the Fukushima nuclear plant in the days after the March disaster in Japan. "There were numerous indications of high radiation levels that can only come from damaged fuel at those kinds of levels, so we felt pretty confident that there was significant fuel damage at the site a few days into the event," said Bill Borchardt, executive director for operations of the U.S. Nuclear Regulatory Commission. His agency also had "suspicions" about the spent fuel pool conditions, Borchardt told reporters after a speech at the Japan Society in New York. Based on that assumption, he said, the commission recommended U.S. residents in Japan remain outside an 80-kilometer radius of the Fukushima Daiichi nuclear power plant, as opposed to the Japanese government's directives for people living in a 20-km radius to evacuate. Tokyo Electric Power Co., the operator of the troubled Fukushima complex, said Tuesday -- more than two months after the disaster -- meltdowns may have occurred in the cores of the Nos. 2 and 3 reactors in addition to the meltdown already found to have taken place at the No. 1 reactor.