Ryoo Yog-Gyu, a Monotoring director of the National Earthquake and Volcano Center, shows seismic waves taking place in North Korea on a screen at the Korea Meteorological Administration center on September 3, 2017 in Seoul, South Korea. (Photo: EPA/TTXVN)

The move came after a report on an earthquake detected in North Korea. According to the organization, the seismic activity took place around 50 km from site of North Korea’s nuclear test earlier this month.

South Korea’s meteorological agency said the earthquake was detected in North Hamgyong province, where the Punggye-ri nuclear site is located. The agency said it was a natural quake but other experts doubted the temblors may be an explosion. The China Earthquake Networks Center said the incident is not a nuclear explosion, but the nature of a natural earthquake.