Threats Posted on White House Facebook Page

Susan Walsh / AP Photo

John Brennan, Assistant to the President for Homeland Security and Counterterrorism, speaks at the Intelligence and National Security Alliance conference in Washington, Wednesday, Sept. 7, 2011.

Threatening messages have been posted on the Facebook page of the White House. "We'll come back U.S.A. One day only 11/9/2011," says one message, featuring a photo of Osama bin Laden. "We'll come to u white house sooooooooooon," says another. "We'll come back 11/9/2011 to kill u all," a third posting reads. Meanwhile, a White House counterterrorism adviser says the Obama administration is taking "very seriously" the threat of a possible Qaeda plot on Sunday's 9/11 anniversary. John Brennan told Fox News Sunday that investigators are trying to piece together the details of an intelligence tip on a possible car-bomb attack that was announced Wednesday. But officials have said they've found no evidence that any of the three suspects has sneaked into the country.