There’s serious activity at a major North Korean nuclear test site

Significant activity has been spotted at North Korea's main atomic test site's west portal -- an as-of-yet unused tunnel complex where little or no activity had been observed over the past several months -- raising the possibility of preparations for a fresh nuclear test, an analysis of new satellite imagery showed Nov. 6.

In the report on the Punggye-ri atomic test site, the North Korea-watching website 38 North said that the imagery, dating from Sept. 8 to Nov. 1, showed "significant movement of equipment, mining carts, material, and netting within the area" of the west portal after Pyongyang's sixth and most powerful nuclear blast on Sept. 3.

That test -- which North Korea has claimed was of a hydrogen bomb -- was held at the site's north portal, where the isolated country's last five nuclear tests were conducted.

According to the imagery, two temporary structures near that portal's entrance believed to be associated with the September test have been removed, and no vehicles, mining equipment, or materials have been observed there since the test.

"While it is not possible to determine the exact purpose of these activities from imagery alone, they could be associated with new nuclear test preparations at the west portal, further maintenance on the west portal in general and/or the abandonment of the north portal," the report said.

While noting little change at the test site's south portal, the report maintained 38 North's long-held stance that tunnels there "have been sufficiently prepared to accommodate a test at any time."

The analysis also said that the available imagery could not corroborate a recent report by TV Asahi citing an unnamed North Korean source said that more than 200 personnel and rescuers had been trapped and feared dead in tunnel collapses at the site.

TV Asahi reported Oct. 31 that the accident had killed scores around Sept. 10. North Korea lashed out at Japan on Nov. 2, dismissing the report as "misinformation" and part of a bid "to secure a pretext for sending the Japan 'Self-Defense Forces' into the Korean peninsula on their own initiative by building up the public opinion over [the] 'nuclear threat' from the DPRK."

The Japan Times could not independently confirm the report, but North Korea rarely acknowledges major accidents, and any incident related to its nuclear program would be especially taboo.

The Nov. 6 analysis by 38 North, however, said the movement of equipment and material at the west portal provided "sufficient evidence that mining personnel have been inside" at least some tunnels at the site.

It said that while the three most recent post-test tremors could have damaged the tunnel networks, there were no observable signs of such a tunnel collapse or intensive rescue or recovery operations outside any of the portals or within any of the support areas.

Related: This is what would happen if North Korea popped off an H-bomb in the Pacific

"While it is possible that the north portal has been at least temporarily abandoned in the aftermath of the Sept. 3 nuclear test, the overall Punggye-ri nuclear test site is neither abandoned nor mothballed," the report concluded. "Significant tunnel related operations continue at the west portal, while the south portal remains in a continuing state of nuclear test readiness."

North Korean Foreign Minister Ri Yong Ho warned in September that Pyongyang may consider conducting "the most powerful detonation" of a hydrogen bomb over the Pacific Ocean amid rising tensions with the United States.

The country's top diplomat made the comment after US President Donald Trump warned that North Korea, which has ramped up its development of nuclear-tipped missiles capable of hitting the United States, would be "totally destroyed" if it threatened the US or its allies.

A senior diplomat with the North's Foreign Ministry said in an Oct. 25 interview with CNN that the threat of an atmospheric test over the Pacific should be taken "literally."

Experts say that conducting such a test would be a way of demonstrating the North's capability of striking the United States with nuclear weapons, since all of its previous tests have been underground.