More than 200 people were killed when a tunnel at North Korea’s Punggye-ri nuclear test site had collapsed after the sixth atomic test in September, according to a Japanese media report.
According to the report published on Tuesday, around 100 workers at the nuclear site were affected by the initial collapse, which took place around September 10.
A second collapse during a rescue operation meant it was possible the death toll could have exceeded 200, it added.
The site was affected by Pyongyang’s sixth nuclear blast on September 3 involving a 100-kiloton hydrogen bomb – seven times more powerful than the atomic bomb dropped by the US on Hiroshima in 1945.
Following the nuclear test on September 3, experts said that a series of tremors and landslides near the nuclear test base destabilised the region, and the Punggye-ri nuclear site may not be used for much longer to test nuclear weapons.
The Korea Meteorological Agency said there is a possibility that radioactive substances may leak out in the future if more nuclear tests are conducted at the site.
South Korea’s National Intelligence Service has said that North Korea was possibly preparing two new tunnels for tests after the test of the hydrogen bomb. The tunnel used for the first nuclear test had been shut down, while a second tunnel had been used for the next five tests.
This second tunnel could have collapsed after the test of the hydrogen bomb, experts said.