Another 100 people subsequently died while attempting to rescue the first group of entombed workers.
Foreign experts had warned a collapse was likely, highlighting the danger of a cloud of radioactive fallout escaping from the site and spreading across “an entire hemisphere”.
The disaster was revealed by Japan’s TV Asahi today, although they could not clarify when the accident and subsequent doomed rescue attempts took place.
They said North Korean sources told them the collapse occurred as workers were working on the new tunnel. A second collapse took place as workers tried to rescue their colleagues.
Punggye-ri was the site of North Korea’s sixth-ever nuclear test on September 3. They tested a huge 100-kiloton explosive which was around seven times as powerful as the bomb dropped on Hiroshima during WW2.
This test is blieved to have badly destabalised the mountainside-based facility.
Speculation is now growing the tragedy could bring a halt to Kim Jong-un’s nuclear ambitions, which he hoped would see the hermit nation rival the capabilities of America.
North Korea’s detonated its first ever H-bomb in September, causing serious damage to the facility’s foundations.
Subsequent small earthquakes have since indicated the area was becoming increasingly unstable.
The Punggye-ri test site is built into Mount Mantap, extending deep within the mountain.
While the exact locations of the nuclear tests themselves remain a mystery, seismologists believe they can pinpoint it to a 100 metre area.
While a test site could be operate safely at such a location, unsophisticated engineers are believe to have increased the risk of disaster with crude drilling techniques.
North Korea news: A satellite image of the Punggye-ri facility
They said a cloud of nuclear fallout could spread across “an entire hemisphere” if the facility collapsed.
The Chinese Academy of Sciences’ Institute of Geology and Geophysics warned: “China cannot sit and wait until the site implodes.
“Our instruments can detect nuclear fallout when it arrives, but it will be too late by then.
“There will be public panic and anger at the government for not taking action.”
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