31/10/2017 09:43 GMT | Updated 31/10/2017 13:49 GMT

North Korea Nuclear Site Tunnel Collapses, Amid Reports As Many As 200 People Killed

Experts suggest the test site may have become 'fatigued and unstable' following nuclear tests.

As many as 200 workers could have been killed after a tunnel under construction at North Korea’s nuclear test site collapsed, Japanese news reports said on Tuesday.

The Yohap News Agency said about 100 people were trapped inside the unfinished tunnel at the Punggye-ri nuclear test site when the incident happened on October 10. 

Japan’s TV Asahi’s said an additional 100 people could have been killed while trying to rescue those trapped south of the Mantapsan mountain.

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North Korea leader Kim John-Un, seen on October 29 inspecting a cosmetics factory

The death toll has not been confirmed. 

The Yohap report suggested experts had warned the test site must have become “fatigued and unstable” following six nuclear tests including the most recent one in September, which featured a 100-kiloton hydrogen bomb.

A series of small-scale earthquakes followed the test and it is has been claimed the tunnel may have been constructed to move the test site to another part of the mountain. 

“If North Korea were to attempt to continue testing under this mountain (such as in the area more to the eastern side), then we would expect to see new tunneling in the future near the North Portal, still under Mt. Mantap,” researchers Frank Pabian and Jack Liu wrote in a report published earlier this month on the North Korea monitoring website 38 North.

Chinese nuclear weapons researcher and chair of the China Nuclear Society Wang Naiyan told the Morning Post a collapse could spark a major environmental disaster.

He said: “We call it ‘taking the roof off’. If the mountain collapses and the hole is exposed, it will let out many bad things.

“A 100 kiloton bomb is a relatively large bomb. The North Korean government should stop the tests as they pose a huge threat not only to North Korea but to other countries, especially China.”

On Monday, the chief of South Korea’s weather agency Korea Meteorological Administration, Nam Jae-cheol, said during a parliamentary meeting that another nuclear blast could trigger a collapse of the North’s mountainous test site and a leak of radioactive materials, the Yohap agency said.