"Analysis of air samples collected on Oct. 11, 2006, detected radioactive debris which confirms that North Korea conducted an underground nuclear explosion ... on Oct. 9, 2006," a statement from the office of the Director of National Intelligence John Negroponte said, adding the explosive yield was less than a kiloton of conventional explosives.
Pyongyang had threatened for a week before it would do the test if the United States did not ease economic sanctions, and followed through with the blast. However, seismic recording led to doubt it had been nuclear in nature until Negroponte's announcement.
The air samples were collected by a military aircraft, officials said without elaborating.
Saturday, the 15-member United Nations Security council voted to impose further sanctions against Pyongyang aimed at stopping the flow of money or materials destined for use in a nuclear weapons program