-Japanese media reports 200 North Koreans died in a tunnel collapse at their nuclear test site.
-In September, North Korea tested a powerful nuclear weapon that experts say rocked the mountain and made it unstable.
-If the test site is totally compromised, the hazardous radioactive material could spread across the region.
After North Korea's most powerful ever nuclear test underground at Punggye-ri in the country's northeast, Japan's TV Asahi reports that up to 200 have been killed in a tunnel collapse.
In early September, North Korea detonated a nuclear device under a mountain that experts assess to have been a hydrogen bomb about ten times more powerful than the first atomic bombs dropped on Japan at the close of World War II.
Since then, satellite imagery has revealed that the mountain above the test site has since suffered a series of landslides, and seismic aftershocks, thought to have resulted from the blast.
North Korean sources told TV Asahi that initially, a tunnel collapsed on 100 workers, and an additional 100 went in to rescue them, only to die themselves under the unstable mountain.
The tunnels in and out of the test site had been damaged previously, and the workers may have been clearing or repairing the tunnels to resume nuclear testing.
Additionally, with the test site compromised, hazardous radioactive material left over from the blast may seep out, which could possibly cause an international incident.
If the debris from the test reaches China, Beijing would see that as an attack on its country, Jenny Town, the assistant director of the US-Korea Institute and a managing editor at 38 North, told previously Business Insider.
Slide 1 of 18: Kim Jong-un and Donald Trump
Slide 2 of 18: North Korea’s Foreign Minister Ri Yong-ho held a press conference in New York, U.S. and stated that Washington had “declared war” on his country when Trump spoke at the U.N. General Assembly on Sept. 19. Ri threatened that the regime could shoot down American warplanes, even if they were not in its airspace, to protect Pyongyang.
Slide 3 of 18: North Korea's leader Kim Jong Un makes a statement regarding U.S. President Donald Trump's speech at the U.N. general assembly, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang September 22, 2017.
Slide 4 of 18: U.S. President Donald Trump addresses the 72nd United Nations General Assembly at U.N. headquarters in New York, U.S., September 19, 2017. REUTERS/Lucas Jackson - HP1ED9J17VGSO
Slide 18 of 18: The United Nations Security Council votes to pass a new sanctions resolution against North Korea during a meeting at U.N. headquarters, Monday, Sept. 11, 2017.
Slide 1 of 18: Kim Jong-un and Donald Trump
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