A U.S.-based North Korea monitoring website says that recent commercial satellite imagery reveals vehicle and personnel tracks at North Korea's Punggye-ri nuclear test site.

In an article and photos published Wednesday, 38 North says vehicle tracks along roads leading to the site's former Main Administrative Support Area as well as personnel foot tracking in the lower courtyard of that area are visible in imagery from November 18 and December 7.

The website said the foot tracking appears to lead to a small assembly area at the base of the stairs leading to a courtyard. 

38 North added, however, that there were no observable signs of activity around closed tunnel areas at the Punggye-ri nuclear test site. 

The website said the precise nature of the vehicle and personnel activity is unclear, but does suggest, at the very least, that personnel remain onsite at the complex as observed in March. 

North Korea announced on May 25 last year that the site had been "completely dismantled" after imploding tunnel entrances. Foreign journalists were invited to witness the destruction from afar, but international inspectors were not invited to verify the physical location.