A think tank says satellite imagery of a site that Iran may have used to work on nuclear arms shows new construction work — possibly a renewed attempt to clean up before an inspection by the U.N.'s nuclear monitor, the International Atomic Energy Agency.

The IAEA has repeatedly cited evidence of apparent attempts to sanitize the Parchin site. But the new report by the Institute for Science and International Security is significant because the IAEA now plans to visit the site soon, as part of the deal between Iran and six world powers focused on limiting Iran's nuclear programs in exchange for the removal of sanctions.

The institute said Thursday the images show a bulldozer or a steamroller, two new structures and other "renewed activity" possibly linked to a "cleanup."