The UN's nuclear watchdog said Wednesday (November 11th) that Iran's explanations over the presence of nuclear material at an undeclared site in the country were "not credible".
Though Iranian authorities provided some information about the site, "the agency informed Iran that it continues to consider Iran's response to be not technically credible", the International Atomic Energy Agency (IAEA) said.
"A full and prompt explanation from Iran regarding the presence of uranium particles of anthropogenic origin... at a location in Iran not declared to the agency is needed," the IAEA said in report.
While the IAEA has not identified the site in question, diplomatic sources have indicated it is in the Turquzabad district of Tehran.
A source familiar with the issue said there was no indication the site had been used for processing uranium but that it could have been used for storing it as late as the end of 2018.
The report did not provide any new information about two separate locations where the IAEA took samples in September and where undeclared nuclear activity may have taken place in the early 2000s.
The analysis of those samples is ongoing.
It confirmed however that Iran's stockpile of enriched uranium is now more than 12 times the limit set down in a 2015 deal with world powers, even if the rate at which the stockpile is expanding has slowed since the last report.
As well as breaching limits on the stockpile amount and enrichment level of uranium laid down in the 2015 Joint Comprehensive Plan of Action (JCPOA), Iran has been using more advanced centrifuges than permitted under the deal.
Wednesday's report confirmed that centrifuges had been installed at an underground part of the Natanz nuclear facility after another part of the site was damaged in an explosion in July which Iran blamed on "sabotage".
On Friday, US Secretary of State Mike Pompeo will start a tour of US allies, including several of Iran's neighbours, during which he is expected to discuss raising further pressure on Tehran in the remaining two months of the Trump administration.