In May 1968, anti-nuclear activists alleged that "Swordfish" had released radioactive coolant water into the harbor of Sasebo, Japan where she was moored at the time. Some sources state that Japanese scientists discovered levels up to twenty times normal background, others, that they could not detect any increase in radioactivity. The Japanese protested the incident to the United States, and Japanese Premier Eisaku Satō stated that U.S. nuclear ships would no longer be allowed to call at Japanese ports unless their safety could be guaranteed.