North Korea parades ICBM
North Korea parades ICBMDamir Sagolj/ Reuters

Chinese geologists warned their North Korean counterparts that the Punggye-ri underground nuclear facility may collapse if future tests are performed, the South China Morning Post reported Friday.

The site is located in the mountains approximately 80 kilometers (50 miles) from the North Korea-China border.

On September 4, just after North Korea confirmed it had tested a hydrogen bomb, researchers from the Chinese Academy of Sciences’ Institute of Geology and Geophysics warned a North Korean delegation in Beijing that the facility was at risk of implosion. Future testing might "blow the top off the mountain," spreading radioactive waste via the wind and cracks created during the implosion.

"“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," a researcher at the country's Peking University told the South China Morning Post.

"The fallout can spread to an entire hemisphere," Institute of Atmospheric Physics Associate Researcher Lan Xiaoqing said.

All of North Korea's tests have been conducted near the same mountain.

China's Foreign Ministry on Thursday said it was not aware the scientists had issued such a warning.

US Secretary of Defense James Mattis on Saturday warned that "any use of nuclear weapons by the North will be met with a massive military response, effective and overwhelming."

Last month, during a visit to New York for the UN General Assembly, North Korean Foreign Minister Ri Yong Ho raised the possibility that North Korea could test a powerful hydrogen bomb over the Pacific Ocean.