New satellite imagery suggests that North Korea is preparing another nuclear test at its Punggye-ri nuclear test site.
The North Korea monitoring Web site 38 North said on Tuesday that satellite photos taken last Thursday and Friday showed a large cargo truck in the South Portal area for the first time, and mining carts and other equipment outside the West Portal.
38 North said this activity suggests the North is preparing those portals for future underground nuclear tests. 
The monitoring site said satellite imagery also showed that landslides from the sixth nuclear test were more severe and extensive than in previous tests.
It estimated the explosive yield from the sixth test at 250 kilotons, which is much larger than an initial estimate of 70 kilotons by the Japanese Defense Ministry.