North Korea is apparently producing plutonium fuel again. Despite far stricter international sanctions, Pyongyang is said to be taking spent fuel from a reactivated reactor at Yongbyon and reprocessing it to make material for its rogue nuclear-warhead program, a senior State Department official, who declined to be named, told Reuters. UN watchdogs had said this week that there were “indications” North Korea had reactivated the facility. “Everything in North Korea is a cause for concern,” the unnamed U.S. official told Reuters reporters. The country conducted its fourth nuclear test in January.