Unusual movements have been reported at a nuclear facility in Yongbyon, North Korea.

A government source said Tuesday that Seoul had confirmed unusual movement by vehicles near the facility’s parking lot and cooling tower last week.

The source said concerned agencies are busy analyzing related information.

According to the source, the movements are likely to be part of preparations to shut down and seal the Yongbyon reactor, citing that a deadline for Pyongyang to close down the facility passed last Saturday.

The source also raised the possibility that the North may be preparing to invite inspectors from the International Atomic Energy Agency.