U.S. intelligence agencies detected an overnight explosion of less than one kiloton in North Korea but have not been able to determine whether it was nuclear or not, a senior intelligence official said Monday. North Korea announced earlier that it had conducted an underground nuclear test, calling it a historic event that would contribute to peace and stability on the Korean peninsula. The U.S. official, speaking on condition of anonymity, told reporters that first-time nuclear tests historically have been several kilotons in magnitude. Other experts around the world reported a seismic event on the Korean peninsula that registered between 3.6 and 4.2 on the Richter scale. Norwegian monitors said their readings indicated an explosion between one and 10 kilotons. Pentagon spokesman Bryan Whitman said it was too early to say whether the blast detected in North Korea was a nuclear explosion. We re evaluating the information that we have as a government. As the president said, we ve not been able to confirm it, he said, referring to a statement earlier Monday by President George W. Bush. Besides seismic data, the U.S. military collects air samples that can be examined for particulates indicative of a nuclear test. However, the relatively small size of the explosion could make positive confirmation of a nuclear test more difficult, officials said.
