I don't know how accurate this is:
Iran Admits Serious Damage to Natanz Nuclear Site, Setting Back Program
A Middle Eastern intelligence official said Israel planted a bomb in a building where advanced centrifuges were being developed
A fire at Iran’s main nuclear fuel enrichment site caused significant damage, setting back the country’s nuclear program by months, the government acknowledged on Sunday, after initially saying the destruction was minor.
A Middle Eastern intelligence official with knowledge of the episode said Israel was responsible for the attack on the Natanz nuclear complex on Thursday, using a powerful bomb. A member of the Islamic Revolutionary Guards Corps who was briefed on the matter also said an explosive was used.
https://www.nytimes.com/2020/07/05/world/middleeast/iran-Natanz-nuclear-damage.html