On one hand Mossad. One the other hand it may have been a major accident, caused by some “political officer” (whatever they call the equivalent in Iran, ok, mullah would do fine) demanding that an impossible deadline be met. Much like what happened to Marshal Mitrofan Nedelin, commander of the USSR Strategic Rocket Forces. He was killed during the test of an R-8 ICBM - demanded that safety procedures be bypassed.
They may have finally figured out that pesky newcular trigger thingy.