U.S. says North Korea test results "inconclusive"

WASHINGTON (Reuters) - Initial U.S. testing to determine whether North Korea fired a nuclear device on Monday proved "inconclusive," said a U.S. official on Friday.

"The first test results came in inconclusive. They did not find anything that could confirm a nuclear device was detonated," said the U.S. official, who declined to be named.

The official said additional tests were being conducted and those results could be known in a couple of days although he had no specific timeline.

North Korea claimed it had conducted a nuclear test on Monday, its second since 2006 and a move that was swiftly condemned worldwide and will likely result in punitive measures against Pyongyang.

Asked if he had any more information on precisely what had transpired on Monday, State Department spokesman Ian Kelly said he did not.

Earlier on Friday, the Vienna-based Comprehensive Test Ban Treaty Organization said absolute proof that Monday's blast was Pyongyang's second nuclear test awaited findings of any radioactive particles and noble gases, expected next week at the earliest.

It said data so far showed Monday's blast resembled both an explosion and an earthquake.

The U.S. Geological Survey reported at the time it had detected a 4.7 magnitude quake in an area close to where the test site was thought to be.

(Reporting by Sue Pleming, editing by Jackie Frank)