US intelligence agencies have questioned the veracity of North Korea's claims on a successful nuclear test saying that the underground blast was more "more fizz than pop".
It is said that elements of the blast have been detected by American and allied sensors as it was set off in an underground tunnel in north-central North Korea with the US intelligence agencies monitoring several such tunnels and in the process not ruling out another test.
Based on preliminary indications American intelligence agencies are not convinced that North Korea carried out its first nuclear test on Monday with officials asserting that conventional high explosives used to create a chain reaction in a plutonium based device did in fact go off but that the readings were short of a typical nuclear detonation.
"We're still evaluating the data, and as more data comes in, we hope to develop a clearer picture," an official "familiar with intelligence reports" has told The Washington Times daily.
"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 official said the Pyongyang test was believed to have been equivalent of several hundred tons of TNT but far short of the several thousand tons of TNT, or kilotons, that are signs of a nuclear blast.
The assessment so far has been that the test was "more fizz than pop."
The White House has already made it clear that it will be several days before it is precisely calculated what it is that took place in North Korea yesterday.