Most likely internal sabotage. Israel has lots of spies and agents inside Iran, who regularly assassinate nuclear scientists. They killed that Hamas chief in a hotel in Tehran, so this type of stuff is nothing for them.
Meanwhile just heard some boom boom in Irani port. Now Iran was FOOLISHLY offering mediation between India-Pak when it's own ass is in danger. Another menace to the world is this MULLA REGIME IRAN! Iran thinks way too high of itself just by supporting terrorists, copy of Pakijeets.