Iran said it’s building a sophisticated new building close to its underground Natanz nuclear site, state TV reported.

The report cited Ali Akbar Salehi, head of the nation’s nuclear agency, as saying the new structure is being built in the wake of a July explosion that damaged a building that housed centrifuge machines.

“Regarding the evil action and sabotage that was carried out, it has been decided to establish a more modern, wider and more comprehensive hall to be constructed in the heart of the mountains around Natanz,” Salehi was quoted as saying.

Natanz hosts the country’s main uranium enrichment facility. In its long underground halls, centrifuges rapidly spin uranium hexafluoride gas to enrich uranium.

Salehi said construction of the new building “has already begun.”

On Sunday, Iran said it had found those who were involved in the alleged sabotage, but said details will be released later.

The July 2 explosion, which foreign media reports have attributed to Israel or the United States, damaged an advanced centrifuge development and assembly plant. Atomic Energy Organization of Iran spokesman Behrouz Kamalvandi said this week that it didn’t interrupt operations but has vowed that Iran would respond if international actors were found to be behind the explosion.

In July Iranian news website “Didban Iran” (“Iran Watch”), tied to the country’s intelligence ministry, reported the Islamic Revolutionary Guard Corps had concluded that the instigator of the blast was Ershad Karimi, a contractor at the site who owns a company, MEHR, that supplies precision measuring equipment.

According to a New York Times report, the blast was most likely the result of a bomb planted at the facility, potentially at a strategic gas line. The report didn’t rule out the possibility that a cyberattack was used to cause a malfunction that led to the explosion.

The explosion was one of a series of mysterious blasts at Iranian strategic sites around the same time, which were largely attributed to either Jerusalem, Washington, or both.

Reports a month ago indicated Iran has been moving to boost uranium enrichment at Natanz. A document from the International Atomic Energy Agency cited by the Bloomberg news agency said new advanced centrifuges were being moved from a pilot facility to a new area of the nuclear facility.

The move appeared to violate the 2015 nuclear agreement Iran signed with world powers, and may show that the alleged sabotage at the plant didn’t significantly set back the nuclear program of Iran. It also suggested the damage to Natanz wasn’t as severe as first believed.

Under the nuclear accord, officially known as the Joint Comprehensive Plan of Action, Iran committed to limiting its nuclear program in exchange for sanctions relief.

But the JCPOA has been on life support since the United States withdrew from it and reimposed unilateral sanctions in 2018.

Iran has since taken small but escalatory steps away from compliance with the agreement, as it presses for the sanctions relief it was promised. Some of those steps are believed to have been at the Natanz nuclear site.

The United States is currently engaged in a likely-doomed bid to renew international sanctions against Iran at the United Nations, despite Trump’s withdrawal from the accord.

The IAEA says Iran enriches uranium to about 4.5% purity — above the terms of the nuclear deal but below weapons-grade levels of 90%. Workers there also have conducted tests on advanced centrifuges, according to the IAEA.