Iran has not yet been able to explain to the International Atomic Energy Agency (IAEA) the presence of uranium particles at one of the undeclared facilities, IAEA Director General Rafael Grossi said on Monday at an online meeting of its board of governors.

The presence of many man-made uranium particles, including altered isotopic particles, at a single site in Iran that was not reported to the agency, is a clear indication that nuclear material or equipment contaminated with nuclear material was at that site. After 18 months, Iran has not provided the necessary, complete, and technically reliable explanation for the presence of these particles, Grossi said in a released statement. 

Due to the lack of a technically credible explanation from Iran, the agency is deeply concerned that undeclared nuclear material may have been present at this undeclared site and that Iran continues to fail to notify such nuclear material under a safeguards agreement.

The IAEA director-general also spoke from three other sites, none of which was announced by Tehran to the agency. Meanwhile, Iran did not answer any of the questions of the IAEA concerning the possible presence of nuclear material on them.

In August 2020, the IAEA, in a joint statement with Iran, noted that they had resolved the issue of access to two disputed Iranian sites. The organization assured that it has no additional questions to Iran and requests for access to other sites. In February 2021, Reuters reported that traces of uranium had been found by IAEA officials at two Iranian sites during inspections conducted in the fall of 2020.