United Nations nuclear inspectors have found traces of radioactive material at Iranian nuclear sites that could indicate work on nuclear weapons, according to a report Saturday.

The Wall Street Journal story cited several unnamed diplomats briefed on the matter, who said the locations in which the material was found contributed to suspicions.

Tehran barred inspectors from accessing those same locations for a number of months last year, it said.

The report did not make clear whether the suspected weapons development was recent or old. The International Atomic Energy Agency and Western intelligence services all believe Iran had a clandestine nuclear weapons program until 2003, though Tehran denies ever attempting to obtain such weapons.

The diplomats noted that they themselves did not have specific knowledge about the details of the findings. They said the IAEA was seeking explanations from Iran, and had not yet updated member states on their findings.

An International Atomic Energy Agency inspector disconnects the connections between the twin cascades for 20% uranium production at Natanz nuclear power plant south of Tehran on January, 20, 2014 (Photo credit: Kazem Ghane/IRNA/AFP)

Last fall Iran allowed IAEA inspectors to visit two sites where the agency suspected undeclared nuclear activity might have taken place in the early 2000s. Their exact locations have not been made public. IAEA Director General Rafael Grossi said at the time that analyzing the samples collected would take several months.

Iran had denied the agency access to the locations last year, prompting the IAEA’s board of governors to pass a resolution in June urging Iran to comply with its requests.

One of the sites was reported to be in Abadeh, south of Isfahan — a location that in September 2019 was flagged by Prime Minister Benjamin Netanyahu as the site of an alleged secret nuclear facility.

Netanyahu said at the time that Iran had tried to destroy the site along with any evidence it had been used to develop nuclear weapons.

The landmark 2015 deal between Iran and the United States, China, Russia, Britain, France, and Germany to curb Tehran’s nuclear ambitions has been largely in tatters since former US president Donald Trump withdrew from it in 2018 and reimposed harsh sanctions on the Islamic Republic.

Iran has since been steadily violating restrictions on the amount of uranium it can enrich and the purity it is allowed to enrich to, and other limits.

Iran recently informed the International Atomic Energy Agency of its plans to increase enrichment to 20 percent, a technical step away from weapons-grade levels of 90%.

It also has said it plans to produce uranium metal, which can be used as a component in nuclear weapons. Iran had signed up to a 15-year ban on “producing or acquiring plutonium or uranium metals or their alloys” under the 2015 accord.

Illustrative: Iran’s alleged atomic warehouse in Turquzabad, Tehran. (YouTube screenshot)

European powers have voiced deep concern over Tehran’s moves, warning it has “no credible civilian use” for the element.

“The production of uranium metal has potentially grave military implications,” said the foreign ministers of Britain, France and Germany, the so-called E3, in a joint statement last month.

A law passed by Iran’s conservative-dominated parliament last month, despite opposition from a reformist government, mandates Iran to discontinue certain international inspections by late February if key conditions are not met, stoking international concerns about a possible expulsion of UN inspectors.

Iran’s foreign ministry on Monday said Tehran does not intend to expel the UN nuclear watchdog’s inspectors.

Tehran has signaled a readiness to engage with US President Joe Biden, who took office on January 20 and who has likewise expressed willingness to return to diplomacy with Tehran.

Iranian President Hassan Rouhani speaks during a cabinet meeting in Tehran, Iran, January 6, 2021. (Iranian Presidency Office via AP)

However, the sides have already sparred publicly, with Washington insisting Tehran must return to compliance to the deal before the US reenters, while Iran says America must first remove all sanctions and rejoin the accord.

Meanwhile, regional US allies including Israel, Saudi Arabia and Gulf states are all expected to strongly oppose a US return to the deal in its original form. Biden has indicated he wishes to address elements outside that worry Middle East nations, including Iran’s ballistic missiles program and its malign regional actions. Tehran has said this is a nonstarter.

Agencies contributed to this report.