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Iran alters nuclear site, US group says

VIENNA — A US institute tracking Iran’s nuclear program says recent satellite images it has analyzed show further major alterations of a military site that the UN has long tried to access to follow up suspicions that Tehran may have used it in attempts to develop atomic arms.

The four photos from satellite company DigitalGlobe and GeoEye were seen by the Associated Press ahead of publication by the Institute for Science and International Security planned for Thursday. The images show what ISIS said was progressive asphalting of an area of the Parchin complex that the UN’s International Atomic Energy Agency has said was a possible location for testing conventional explosive triggers for a nuclear blast.

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Experts of the UN nuclear watchdog organization met Iranian negotiators 10 times during 18 months in sessions ending earlier this year in futile attempts to gain access to the site and test Tehran’s insistence that it was a conventional military area with no link to nuclear tests.

Iran has said the asphalting is part of regular maintenance and road work. But with its probe blocked — and signs of other activity — IAEA concerns have grown that it might be an attempt to cover up work on a weapons program while it keeps away inspectors.

Asphalting the area would make it more difficult to take soil samples in the search for traces of testing. Beyond the asphalt work, IAEA chief Yukiya Amano said earlier this year he was concerned about soil removal, and ‘‘possible dismantling of infrastructures.” Because of such alleged steps, he said ‘‘it may no longer be possible to find anything even if we have access to the site.’’

Olli Heinonen, the previous head of the IAEA’s Iran inquiry, suggested the paved area resembles a parking facility.

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