Recent satellite images appear to show that specialized railcars are being moved at North Korea's main nuclear site.
According to the U.S.-based North Korea-monitoring website 38 North on Sunday, three railcars that arrived at the Yeongbyeon Nuclear Center by February 10th had departed by the end of the month.
The website noted the movement suggests the North could have been transporting re-agents used in nuclear fuel production or waste handling and decontamination processes.
However, there was no evidence the transported products were radioactive.
The website added there was some fresh snowfall on some of the facilities but noted that cannot prove the suspension of its operation.