A tunnel at North Korea’s mountainous nuclear test site reportedly collapsed days after the secretive state’s sixth nuclear test in September, killing up to 200 people, according to a report by Japanese broadcaster TV Asahi.
Citing the same report, South Korea’s Yonhap news agency reported about 100 people were in the tunnel at the Punggye-ri test site when it caved in, while up to another 100 people died trying to rescue their co-workers when a second collapse occurred.
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A spokesperson for South Korea’s unification ministry told Agence France-Presse they had no information on the reported tunnel collapse.
“We are aware of the report but do not know anything about it,” the spokesperson said.
In the days after the Sept. 3 test, which was said to have been a hydrogen bomb designed to be mounted on a newly developed intercontinental ballistic missile, experts said the detonation caused several landslides at the country’s only known test site.
U.S.-based North Korean watchdog 38 North obtained satellite images the day after the test, which suggested landslides had occurred.
“These disturbances are more numerous and widespread than what we have seen from any of the five tests North Korea previously conducted,” the watchdog noted at the time. “There does not appear to be any evidence of a collapse crater, as might have been suggested from the post-test tremor.”
The U.S. Geological Survey (USGS) recorded a seismic event measuring 6.3 in magnitude near the Punggye-ri test site. A smaller 4.1 magnitude event was recorded about eight and half minutes later, suggesting a structural collapse of sorts.
“Among the possibilities for such an event, the USGS proffered that it was a post-test ‘tunnel collapse,’ but it could also have been a ‘chimney collapse,’ caused by the area above the test cavity collapsing downward forming an upward shifting cavity known as a chimney,” the watchdog suggested.
The smaller event could have been a “landslide or other earth movement induced by the large test.” The watchdog added that “such a post-test event of this magnitude increases the likelihood” of the release of radiation.
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Kim Jong Un and his regime are believed to have carried out at least five of the country’s nuke tests at the same Punggye-ri test site, which prompted a Chinese scientist to warn days after the test that the next one could collapse the mountain resulting in a massive radiation leak.
Wang Naiyan of the China Institute of Atomic Energy told the South China Morning Post in September if such a collapse should happen, it would pose a radiation threat to both North Korea and regions of bordering China.
“We call it ‘taking the roof off,”’ Naiyan told the newspaper. “If the mountain collapses and the hole is exposed, it will let out many bad things.”
The Japanese broadcaster reported the tunnel collapse occurred around Sept 10.
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On Sept. 12, South Korea’s national public broadcaster KBS, reported North Korea had sent workers into a tunnel at the test site while 38 North reported activity at the site on Sept. 8.
“Such activity, coming shortly after the largest underground nuclear test conducted at Punggye-ri to date (via the North Portal), suggests that onsite work could now be changing focus to further prepare those other portals for future underground nuclear testing,” the watchdog noted at the time.
–with a file from Reuters
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