Ricin was also sent to the White House in November, kept secret until now, but confirmed. That was a vial of liquid, this is powder.
FBI Says Ricin Also Mailed to White House in Nov.
Powder Found in Frist's Senate Office Is Confirmed
http://www.washingtonpost.com/wp-dyn/articles/A8403-2004Feb3.html The FBI said today that a letter containing a vial of the poison ricin was mailed in November to the White House. That disclosure followed an announcement by Senate Majority Leader Bill Frist (R-Tenn.) that authorities have confirmed the white powder found in a Senate office building yesterday was ricin.
The White House incident had been kept secret until now. The letter, officials said, never reached the White House because it was intercepted at an offsite mail facility.
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I wonder how hard it is to make ricin into powder form.