"Davani confirmed on Monday that the attack last July [in Natanz] was also carried out with explosives that were smuggled into a centrifuge assembly facility at the site, with the explosives embedded in a heavy table that was brought into the facility. (...) The Iranian official stressed that such an operation takes years, saying "the design of the enemy was very beautiful."

https://m.jpost.com/middle-east/natanz-attack-destroyed-facility-50-meters-underground-664979