If this were the anthrax mailer, I doubt very much that he'd agree to a "consensual search." This would appear to be somebody looking to clear himself; from the FBI's point of view, they would like to appear to be making some progress on the case.
Moreover, even if somebody else from Ft. Detrick turns out to be implicated in some fashion, that does not make this an act of domestic terrorism or in any way confirm Barbara Hatch Rosenberg's tireless speculations. The anthrax sent by Islamic terrorists could well be derived from anthrax stolen from a U.S. lab. (Being of the Ames strain, it is derived, directly or indirectly, from anthrax obtained in the U.S. either legitimately or illegitimately. It might have been from an academic research lab or from a military lab; it probably was not collected in the wild. But, after being obtained, the anthrax was likely grown in large quantities elsewhere and weaponized elsewhere before being provided to the terrorists; finding out about that would be much more interesting than discovering the original source of the anthrax sample that was used.)
1. With regard to today’s search they say this was one of two dozen like it.
2. They have found no evidence linking the person to the anthrax scare.
(Yes, I know, I know, who believes anything the FBI says)