Seoul's Yonhap news agency cited an unidentified South Korean official Tuesday as saying that intelligence authorities in Seoul and Washington reached the conclusion after scrutinizing about 10 atomic facilities in North Korea.
North Korea vowed in April to restart its nuclear facilities in anger over a U.N. rebuke of its long-range rocket launch.
Pyongyang claimed the launch was a peaceful attempt to put a satellite into orbit, but the liftoff was condemned as a test of the North's long-range missile technology.
