You can’t make this up: a test blast at a North Korean nuclear facility went off the rails – killing as many as 200 laborers.

Earlier this month, North Korea conducted its sixth underground nuclear test at the Punggye-ri test site deep inside Mount Matap. The resulting blast led to the collapse of a nearby mine shaft.

About 100 workers were present in the area buried by the collapse. Another 100 laborers were sent into the partially-collapsed tunnel to rescue their colleagues, but they died when the rest of the shaft gave way.

Western intelligence has not established an exact date for this test, but North Korea claims that the bomb, their most potent yet, created a 6.1 magnitude earthquake, causing widespread destruction and likely additional casualties.

Scientists from China and South Korea have warned North Korea that Mount Matap could eventually wholly collapse due to the nuclear tests, which could devastate the region by releasing massive amounts of radiation.

However, despite the warnings and the latest collapse, Kim Jong-un reportedly has no plans to relocate his regime’s nuclear test facility.