The Institute for Science and International Security says North Korea is continuing to expand a centrifuge plant located inside the Yongbyon nuclear complex.
 
The Washington-based institute said in a report on Wednesday that construction activities are continuing in the area of the centrifuge plant located on the southern border of the Yongbyon site. The report made the assessment after comparing commercial satellite imagery taken on June 30 with images taken earlier in April.
 
The report said possible construction objects detected in the April satellite images have been removed. It added that a new roof, seemingly connecting two buildings that were previously separated by a small road, is being built immediately north-west of the main centrifuge building. It said roof activity is also taking place at several other buildings on site.
 
The report also said a train connected to three flat cars carrying possible construction material is clearly visible on the tracks.
 
However, the institute stressed that it is unclear whether North Korea has finished the expansion of the centrifuge plant.
 
The institute said the June 30 satellite imagery, combined with procurement data obtained by the institute, suggests that North Korea is emphasizing the production of weapon-grade plutonium and enriched uranium for its nuclear weapons program.