Terrorists are not going to give a warning regarding a dirty bomb being used. They will just do it.
Unless AQ can't lay its hands on one and decides that scaring the snot out of everyone is the next best thing. Sigh.
Have terrorrists issued a threat, or is non-Bostonian law enforcement/FBI/HLS giving a heads up? It may not be the Al Quesos.
From what I've heard on abc radio, it was the guy who smuggled them in who has been calling from Mexico to say that they're in the country.