Research by Chinese geologists shows the mountain above North Korea’s main nuclear test site has collapsed, rendering it unsafe for further testing and requiring that it be monitored for any leaking radiation.

The findings by the scientists at the University of Science and Technology of China may shed new light on North Korean President Kim Jong Un’s announcement that his country was ceasing its testing program ahead of planned summit meetings with South Korean President Moon Jae-in and US President Donald Trump.

Nuclear explosions release enormous amounts of heat and energy, and the North’s largest test in September was believed early on to have rendered the site in northeastern North Korea unstable.