Preliminary US tests on air samples taken over North Korea found radioactive debris, lending additional credence to Pyongyang's claim it exploded a nuclear device, according to a draft report distributed to members of US Congress.
The report drafted by the office of the Director of National Intelligence (DNI) John Negroponte and distributed to members of US Congress on late Friday, was initially quoted by CNN.
But the DNI's office said the report was not an official statement, but rather a draft report based on preliminary information as part of consultations with Congress.
A spokesperson for the office, Chad Kolton, emphasised to DPA that a report has not been released to the public because it does not contain a final analysis.
Earlier on Friday, US media reports said that US tests failed to find radioactive evidence. But reacting to that report, a US intelligence official said an initial air sample alone does not allow analysts to draw a definitive conclusion about whether the apparent North Korea test was positive.
"We are still looking into this and it will be several days until we know what happened," a second official in the US intelligence community told DPA.
The statement distributed to Congress said that preliminary analysis of air samples detected "radioactive debris consistent with a North Korea nuclear test," according to CNN, which read the statement on air.
The US Air Force flew a WC-135 to collect air samples from the region on Wednesday, two days after North Korea's announcement.
The statement said the debris was consistent with North Korea's claimed test "in the vicinity of Punggye."
In the days following the claimed test, the US remained skeptical, pending its own confirmation.
The UN Security Council is poised to pass on Saturday strong sanctions against North Korea for the test, after days of negotiations to convince China and Russia that such steps were necessary.