“White House officials said Western intelligence agencies have been tracking the facility for years. Obama said officials from the United States, France and Britain briefed the IAEA in Vienna on Thursday on what they knew about the facility. The three heads of state decided to publicly disclose the existence of the facility after learning that Iran had become aware the site was no longer a secret.”
from
http://www.washingtonpost.com/wp-dyn/content/article/2009/09/25/AR2009092500289_pf.html
http://www.reuters.com/article/topNews/idUSSUM00011520090925
Not really a “secret” site if it had been known and warned about for “years”. I think Iran knew we knew but just didn't give a damn and still don't give a damn.