The head of the UN's nuclear watchdog says environmental samples have been taken at a sensitive military site in Iran.
Yukiya Amano, the chief of the International Atomic Energy Agency (IAEA) said in Tehran on September 21 that "the Iranian side played a part in the sample-taking process by swiping samples" at the controversial military site Parchin, outside of Tehran.
He said his agency had made "significant progress" in its investigation of Tehran's past activities at the site.
Amano said Iran's role in the probe of the site and its taking of dust samples at Parchin met IAEA standards.
He said the process was "carried out under our responsibility and monitoring."
A spokesman for Iran's nuclear agency, Behruz Kamalvandi, said "the IAEA team was not in the facility" when the samples were taken, which was in the past week.
IAEA chief inspector Tero Varjoranta said in Vienna that video monitoring was used to confirm the taking of the samples by the Iranians.
The dust samples will be analyzed for traces of nuclear elements that could indicate if high-explosive experiments were conducted at Parchin.
Amano said he had visited the building in Parchin allegedly used for experiments and that it had been recently renovated and stripped of all equipment.
He said that "extensive work" at the building, which has been ongoing since 2012, "undermines the agency's ability to conduct effective verification procedures."
U.S. and other Western countries charge that Iran has carried out work on building nuclear weapons.
Iran says its nuclear program is entirely for peaceful purposes.