U.S. AUTHORITIES HAVE NOT YET DETERMINED WHO WAS RESPONSIBLE FOR A SERIES OF ANTHRAX ATTACKS THAT KILLED FIVE AMERICANS IN LATE 2001, PRESIDENT GEORGE W. BUSH'S TOP COUNTER-TERRORISM ADVISOR SAID TUESDAY. “OBVIOUSLY, THAT'S AN ONGOING INVESTIGATION,” FRANCES TOWNSEND TOLD REPORTERS DURING A WHITE HOUSE BRIEFING ON THE NEWLY DECLASSIFIED FINDINGS OF A NATIONAL INTELLIGENCE ESTIMATE (NIE) ON TERRORIST THREATS TO THE UNITED STATES. ASKED WHETHER THE ANTHRAX MAILINGS, WHICH BEGAN WITH A LETTER POSTMARKED SEPTEMBER 18, 2001, WERE CONSIDERED A TERRORIST ATTACK, TOWNSEND REPLIED, “IT DOES IN MY MIND.” FIVE PEOPLE DIED AFTER LETTERS CONTAINING ANTHRAX SPORES WERE SENT TO SEVERAL NEWS MEDIA OFFICES AND TWO DEMOCRATIC SENATORS.