US: No radiation detected after North Korean test

Results from an initial air sampling after North Norea's announced nuclear test showed no evidence of radioactive particles that would be expected from a successful nuclear detonation, a US government intelligence official said Friday. The test results do not necessarily mean the North Korean blast was not a nuclear explosion, the official said, speaking on condition of anonymity because he was not authorized to disclose the sampling results. The US government remains uncertain of the nature of the underground explosion, officials said, although the result from air sampling tends to reinforce the indication that the test blast was not entirely successful.