I thought that part of the deal with Europe last October was that Iran had to shut down the centifuges, but then Iran warned the world that they would start them up again whenever they felt like doing so. Maybe not?
Either way, the Americans know. It can't be hidden.
I am aware that the Iranian plan was to use the 20 or so test centifuges to mask the operation of the thousands other centifuges. If you're right, then that is very bad.
We may not know when they have the bomb until they detonate one.