North Korea left about 300 troops behind at its nuclear test site in Punggye-ri, North Hamgyong Province to guard the facility when it pulled out a military unit, the Asahi Shimbun reported Tuesday.
Most of the 1,200 troops of the regiment were relocated early last month, a source told the daily, but 300 were left behind. Their task is "to prevent residual radioactive and other materials from being lost," the source said.
The regime promised to halt nuclear and missile tests and close down the nuclear test site last week.
The daily speculated that the North wants to try to keep a lid on the site as the Punggye-ri nuclear test site could be a barometer to gauge the level of its nuclear development.
The website 38 North at John Hopkins University on Monday said the site "is still, as far as we can tell, fully operational."
"One area at the site -- the North Portal, located at Mount Mantap where the last five underground nuclear tests had been conducted -- was apparently abandoned," it said. "However, significant new tunneling was noted at the West Portal, another area of the site, up through early March 2018. That renewed tunneling was curtailed by mid-March, but not entirely stopped through early April, suggesting that either the tunnel was complete and ready for future renewed testing or that the slowdown simply mirrored the ongoing political changes underway."
"Another potential test tunnel, accessible via the South Portal, includes a primary and secondary entrance. Complete for several years now, that area also remains suitable for future underground nuclear tests," it added.
North Korea's nuclear test site in Punggye-ri, North Hamgyong Province, in satellite photos taken on March 2 and March 17 /Courtesy of 38 North