September 10, 2001 (M): US officials later admit American agents had infiltrated al-Qaeda cells in the US, though how many and how long they had been in al-Qaeda remains a mystery. On this day, electronic intercepts connected to these undercover agents hear messages such as: "Watch the news" and "Tomorrow will be a great day for us." As to why this didn't lead to boosted security or warnings the next day, officials call these leads "needles in a haystack." What other leads may have come from this prior to this day are not revealed. [USA Today, 6/4/02] At least until February 2002, the official story was that the "CIA failed to penetrate al-Qaeda with a single agent." [ABC News, 2/18/02] FBI Director Mueller later claims "To this day we have found no one in the United States except the actual hijackers who knew of the plot" (see June 18, 2002) but what about the people in these penetrated cells giving these messages?