Fox News: Federal officials responded to a bomb threat at NPR in Washington, D.C., on Monday, nearly a week after the controversial firing of Juan Williams, the FBI tells Fox News. Federal agents with the Joint Terrorism Task Force collected a letter that was received in the mail, the FBI said Tuesday. It is now in the bureau's custody. There is no word on what was said in the letter. The Washington Post reports that NPR warned its employees about a general "security threat" in a staff memo Monday.