An official in France's Atomic Energy Commission reported that they estimated the blast was "about or less than a kiloton" and expressed uncertainty about whether or not the blast was actually nuclear. There have been various large planned and unplanned non-nuclear explosions comparable in yield to small nuclear detonations, such as the U.S. "Minor Scale" explosion from 1985, which used conventional explosives to simulate a 4 kiloton detonation. According to the "Washington Times" anonymous U.S. intelligence sources speculated there "was a seismic event that registered about 4 on the Richter scale, but it still isn't clear if it was a nuclear test. You can get that kind of seismic reading from high explosives". "The Wall Street Journal" explains that this blast was equivalent to the explosive force of about US$100,000 worth of ammonium nitrate. International experts have said that it will take some time to confirm whether it was a successful nuclear test, as North Korea claimed, or an unsuccessful one ("fizzle"), or perhaps not even a nuclear test at all.