Qaeda Letters Are Said to Show Pre-9/11 Anthrax Plans WASHINGTON, May 20 -Al Qaeda operatives in Afghanistan began to assemble the equipment necessary to build a rudimentary biological weapons laboratory before the Sept. 11, 2001, attacks, letters released by the Defense Department show.... The letters are among the documents recovered in late 2001 after the invasion of Afghanistan that United States intelligence officials have frequently cited as evidence that Al Qaeda was working to develop biological weapons.The letters...detail a visit by an unnamed Qaeda scientist to a laboratory at an unspecified location where he was shown "a special confidential room"...