Apocalypse111 writes, "According to CNN.com, air samples taken over North Korea have not yet shown any radiation from the event on Monday that North Korea claims was a nuclear test. This is not definitive proof that the event was non-nuclear, as it may either have been so small and deep that it did not let any radioactive debris escape, or perhaps the North Koreans sealed the site." Furthering speculation over whether North Korea has actually exploded a nuclear device, vk38 writes to point out a (free) article in today's Wall Street Journal claiming that the blast could have been
set off by exploding fertilizer (ammonium nitrate). The article points to the
Texas City disaster of 1947, in which 7,700 tons of ammonium nitrate exploded in the hold of a ship with the estimated power of 2 to 4 kilotons of TNT.
Update: 10/14 08:03 GMT by Z : The story at CNN has been updated: "A preliminary analysis of air samples from North Korea shows 'radioactive debris consistent with a North Korea nuclear test,' according to a statement from the office of the top U.S. intelligence official."