Iran has "resolved" one of three cases raised by the UN watchdog as possible evidence it had not declared all its past nuclear activities, Iranian media reported Tuesday.
The reports came just days before the board of governors of the International Atomic Energy Agency is due to meet to review progress in addressing the watchdog's remaining concerns.
The IAEA had reported the discovery of traces of radioactive material at three sites not declared by Iran as having hosted past nuclear activity in a blow to efforts to restore a landmark 2015 deal between Tehran and major powers.
"With the improvement of interactions between Iran and the IAEA... the case related to one of the agency's alleged sites -- Abadeh -- has been resolved," Iran's Fars news agency reported.
"This concludes the agency's inquiry into one of the three alleged locations raised," it added.
The Marivan site in Abadeh county in the southern province of Fars is the first of the three sites to be addressed under a work plan agreed by Iran and the IAEA in March last year.
The other two sites are Varamin and Turquzabad.
The IAEA's concerns about the sites are one of the remaining obstacles to the revival of the 2015 nuclear deal, which was left in tatters by the unilateral withdrawal of the United States in 2018.
Fars also reported that Iran had addressed IAEA concerns about the discovery of uranium enriched to close to the level required for a nuclear warhead.
Iran said the enrichment of the sample to 83.7 percent was likely due to "unintended fluctuations" in the enrichment process as it had never set out to enrich uranium to more than 60 percent, still well short of the 90 percent needed for a warhead.
Iran has always denied any ambition to develop a nuclear weapons capability, insisting its activities are entirely peaceful.