Before the Senate Offices, Ricin-Laced Letter Was Also Sent to White House Feb. 3 — As federal investigators try to trace the origin of suspected ricin found Monday in the office of Senate Majority Leader Bill Frist, ABCNEWS has learned of an earlier, undisclosed incident in which a ricin-laced letter was intercepted on its way to the White House. In November, a letter postmarked Chattanooga, Tenn., and addressed to the White House was intercepted at an off-site mail sorting facility in the Washington area, sources told ABCNEWS. The powdery substance in the letter tested positive for ricin. However, the tests...