Iran has secretly stocked enriched uranium for four nuclear bombs
The Wisconsin Project quotes the International Atomic Energy Agency's May 2011 report that one of its seals was broken in the "feed and withdrawal area" of the Natanz enrichment plant.

This means that Iran took action to conceal the real amount of is enriched uranium stockpile from the nuclear watchdog and the fact, as Wisconsin reports, that it has accumulated enough material for building four nuclear bombs. Its steady progress will go undetected until the next IAEA inventory in October or November.