The UN nuclear watchdog confirmed Thursday that IDF strikes had hit Iran’s partially built Khondab Heavy Water Research Reactor and damaged the nearby plant that makes heavy water, a component used in nuclear react.

“IAEA has information the Khondab (former Arak) heavy water research reactor, under construction, was hit. It was not operational and contained no nuclear material, so no radiological effects,” the International Atomic Energy Agency said in a post on X.

In its first statement on the attack in central Iran, the IAEA said it had no information indicating the nearby plant that produces heavy water had been hit. The agency later issued a statement revising that assessment.

“While damage to the nearby Heavy Water Production Plant was initially not visible, it is now assessed that key buildings at the facility were damaged, including the distillation unit,” the IAEA statement said.

The strike on the Arak heavy water reactor came a week into Israel’s campaign of airstrikes against the Islamic Republic’s nuclear program and military leadership.

Heavy water reactors use heavy water, also known as deuterium oxide, as a moderator, a material that slows down fast-moving neutrons released during the nuclear fission process that generates heat in the reactor.

The Arak facility that was struck overnight Thursday was originally designed in a way that would make it capable of easily producing plutonium, which could be used to produce nuclear arms.

Under a 2015 deal with major powers, the heavy water plant was redesigned to reduce the nuclear weaponization risk and its core was removed and filled with concrete. Iran had informed the Vienna-based International Atomic Energy Agency the reactor would start operation in 2026.

The IDF, which issued a warning to residents of the area to evacuate ahead of the strike, said the attack on Arak “targeted the component intended for plutonium production, in order to prevent the reactor from being restored and used for nuclear weapons development.”

Iran’s leaders, who are sworn to destroy Israel, publicly deny seeking nuclear arms, but have amassed highly enrich uranium that has no civilian use, according to an IAEA report last month.

Emanuel Fabian contributed to this report.