The Central Intelligence Agency has told Congress that it now believes that North Korea has mastered the technology of turning its nuclear fuel into functioning weapons, without having to prove their effectiveness through nuclear tests. The C.I.A. report goes beyond previous public statements suggesting that North Korea built one or two weapons in the early 1990’s, a figure many intelligence experts believe has risen in the last few months. Those statements carried the presumption that the North had developed the technology to detonate weapons, but in background briefings, some American and Asian intelligence officials expressed doubts. They said that in the absence of a North Korean nuclear test, there was no way to be certain of its capabilities. Now those doubts appear to be gone. But the reason why is still a mystery, perhaps buried in a classified annex that the C.I.A. also sent to Congress. Full Story