A nuclear expert has downplayed a CNN report that said activity suspected of being nuclear warhead production has been spotted at a previously unknown facility in Wollo-ri, Pyongyang.

Former deputy director general of the International Atomic Energy Agency(IAEA), Olli Heinonen, told the Voice of America on Friday that there is little possibility that there’s such a facility in that region.  

He said if there was a nuclear-related site there, there should be more visible air exhaust chimneys apart from storage of nuclear material such as uranium.  

Heinonen said that signatures would be stronger if uranium or plutonium warheads were being manufactured. He added that there have been no signs of arrangements related to highly explosive components in warheads either.

He went on to say that there is no hard evidence in the report suggesting that it is a nuclear-related site, adding that generally all military related sites have fences around them. 

Earlier on Wednesday, CNN said it acquired satellite imagery showing activity, suspected of being nuclear warhead production, at a previously undeclared facility in Wollo-ri. 

Quoting Jeffrey Lewis, a professor at the Middlebury Institute, CNN said the facility is "very active" and it hadn't slowed down even during Pyongyang's now-stalled denuclearization dialogue with Washington.