A series of earthquakes, which is unusual in the area, have been recorded, while a massive tunnel collapse at the site was also detected.

Japan’s Asahi TV on Tuesday reported that at least 200 people died and about 100 people were trapped inside in the collapsed tunnel, without providing information on when it happened.

The news follows Seoul’s weather agency Korea Meteorological Administration chief, Nam Jae-cheol’s remarks that another detonation could possibly prompt a collapse of the test site and spill radioactive materials, during a parliamentary audit here on Monday.

“Based on our analysis of satellite imagery, we judge that there is a hollow space, which measures about 60 to 100 meters (in length), at the bottom of Mount Mantap in the Punggye-ri site,” Nam told lawmakers. “So, should another nuke test occur, there is the possibility (of a collapse).”

Concerned about nuclear waste contamination, Chinese scientists reportedly warned Pyongyang to relocate the test site, as the mountain range about 80 kilometers away from the North Korea-China border is at risk of collapse, Hong Kong’s South China Morning Post said. If the site deteriorates, the nuclear waste spill may seep through the border and spoil Chinese soil.

North Korea’s sixth and latest nuclear test on Sept. 3, which is also referred to as its strongest yet, may have dealt a heavy blow to its topography. The South Korean Meteorological Administration said the test caused an artificial magnitude 5.7 earthquake, while the US Geological Survey and the Chinese government measured a seismic activity of 6.3. Smaller tremors followed, which many saw as aftershocks of the detonation.

But a US think tank claimed that “for the time being,” Pyongyang has no plans to abandon the Punggye-ri test site, “given the presence of additional test portals.” Although substantial damage to the tunnels is suspected, similar nuclear tests conducted at the US Nevada Test Site and former Soviet nuclear test sites did not lead to site abandonment, an analysis by 38 North, at the US-Korea Institute at Johns Hopkins School of Advanced International Studies said.

Meanwhile, experts here expressed doubt over the possibility of a North Korean provocation triggered by the signs of its crumbling test site, to sustain the current level of tension — despite its longest hiatus in military provocations in recent months.

“North Korea currently has two options regarding military provocations — launching an intercontinental ballistic missile test or nuclear test,” Koh Yoo-hwan, a professor of North Korean studies at Dongguk University said.

“However, if its nuclear test site (of Punggye-ri) is exhausted there won’t be another nuclear experiment any time soon,” he said.

On the possibility of an atmospheric nuclear test, Koh said that it entails a massive risk at the moment with US President Donald Trump’s scheduled visit to South Korea next week. At the UN General Assembly in New York last month, North Korean Foreign Minister Ri Yong-ho told reporters that Pyongyang is considering dropping a hydrogen bomb in the Pacific Ocean.

“The North will think twice before launching any sort of military provocation with President Trump’s Asia tour. It will weigh the current situation and keep close tabs on how the situation shifts after the tour,” Koh added.

Seoul’s Unification Ministry said Wednesday that it will probe further the Asahi TV report and plans to announce relevant reports by the end of the year.