The White House just held a press conference in which they confirmed that a letter addressed to President Obama has tested positive for richin. There is no indication that this letter is connected to the bombings in Boston.

The letter was intercepted at an off-site facility before it arrived at the White House. Yesterday authorities intercepted a letter at another off-site processing facility that had sent to Sen. Roger Wicker (R) which also tested positive for ricin.

Ricin is a highly toxic protein obtained from the pressed seeds of the castor-oil plant. It is considered a biotoxin.