claiming. catherine herridge has been investigating. she is live in washington. catherine? >> well, thanks, shep. congressman rushhold says as many as seven anthrax letters were mailed from his new jersey district. he saw the fbi investigation upclose and he said it did not inspire confidence, quote. director fbi robert mueller acknowledged the case against ivins was almost entirely circumstantial it does not have any direct physical evans tieing ivins to the attack. this letter called the quantico letter may be the missing link in that case. sent in the fall of 2001, the same time frame as the anthrax letters and warned of a bioterror attack by a arab scientist. quote. this guy is potential terrorist. this guy has access to many dangerous biological poisons. >> i showed them, statement by statement how they are similar and how they might be coming from the same source. >> scientist dr. assad was cleared by the fbi in the