All of the 15,000 centrifuges operating at Iran’s largest uranium enrichment facility in Natanz were badly damaged or destroyed by last week’s Israeli attack, the International Atomic Energy Agency said on Monday.

“Our assessment is that with this sudden loss of external power, in great probability the centrifuges have been severely damaged if not destroyed altogether,” said IAEA Director Rafael Grossi during an interview with the BBC.

“I think there has been damage inside” the underground portion of the facility, Grossi continued. The above-ground enrichment plant at Natanz was destroyed during the attack.