A former deputy chief of the International Atomic Energy Agency(IAEA) has claimed that North Korea is maintaining its Punggye-ri nuclear test site, of which it destroyed some of the tunnels in 2018.  

Olli Heinonen, currently a fellow at the Stimson Center, issued the assessment in an interview with the Voice of America, citing recent satellite imagery of the site.

Heinonen reportedly said that trails of cars and the clearing of snow indicate that North Korea is doing some kind of maintenance on some buildings. 

The former IAEA official said that these activities are more than just monitoring and the North keeps certain buildings in condition. He added it's not a lot of people, but quite a few buildings seem to be in use.

Heinonen, however, projected that it will be difficult for the North to conduct a nuclear test at the site right away, citing a lot of possible damage to the integrity of the rock and mountain around the site by a very powerful test in the past.