A tunnel at North Korea's nuclear test site collapsed after Pyongyang's sixth atomic test in September, possibly killing more than 200 people.
About 100 workers at the nuclear site were affected by the initial collapse.
The second collapse during a rescue operation meant it was possible the death toll could have exceeded 200.
Experts have said a series of tremors and landslides near the nuclear test base probably mean the country's sixth and largest blast on September 3 has destabilized the region, and the nuclear site may not be used for much longer to test nuclear weapons.
Source: Stuff.co
