Iran's Atomic Energy Organisation (IAEO) has blamed a massive fire that broke out at the Natanz nuclear facility last month on sabotage.
"Security investigations have confirmed that this was an act of sabotage, and what is clear is that an explosion took place at Natanz," IAEO spokesman Behrouz Kamalvandi said.
Kamalvandi gave no details about the exact cause of the explosion or who was behind it, saying only that it will be announced "in due course".
The fire broke out at a warehouse at the Natanz facility on 2 July. Natanz is one of Iran's two uranium enrichment sites that were being regularly inspected by UN nuclear watchdog the IAEA under the terms of the 2015 Joint Comprehensive Plan of Action (JCPOA) nuclear deal with Iran.
The JCPOA freed Tehran of US and EU sanctions, allowing the country to export its crude and oil products unhindered. But Washington's unilateral exit from the deal in May 2018 led to US sanctions being reimposed later that year and prompted Tehran to begin winding down its own compliance with its JCPOA commitments. Iran took its "fifth and final" step in January when it removed all JCPOA restrictions placed on the number of centrifuges installed at Natanz and at Fordow, Iran's second uranium enrichment site.
In the days following the Natanz incident, Iranian authorities said the fire had caused significant damage and "may cause a slowdown or interruption" to the IAEO's work. The warehouse in question was under construction and was meant to house critical machinery that can produce advanced centrifuges.
The IAEA's director general Rafael Grossi is due to visit Iran today to discuss the agency's ongoing co-operation with Tehran, with a focus on securing access for the IAEA's inspectors to two sites that it suspects could have been involved in the development of nuclear weapons in the past.
"My objective is that my meetings in Tehran will lead to concrete progress in addressing the outstanding questions that the agency has related to safeguards in Iran and, in particular, to resolve the issue of access," Grossi said over the weekend.
The IAEA stepped up pressure on Tehran in June by formally calling on the country to once again grant its inspectors access to Natanz and other locations, and to clarify possible undeclared nuclear material and nuclear-related activities.
Kamalvandi acknowledged the two sites in question, saying one is in the city of Shahreza in Iran's central Isfahan province, and the other is near Tehran.
"From the beginning, Iran has not opposed access to its nuclear facilities. But we believe that the IAEA's questions must be based on serious principles, evidence and reasons," Kamalvandi said. "When the IAEA has a question for countries, it is the inalienable right of that country to demand from the agency the basics and documents related to those questions," he said.
