[Update- 4/17/13] Second Letter Sent To U.S. Senate Tested Positive For Ricin Poison - Poison Letter Also Sent To Obama
Original post below
Multiple media outlets, including CNN, Chicago-Sun Times and NPR, are confirming that a letter sent to Senator Roger Wicker (R-MS), has tested positive for Ricin poison.
The envelope was intercepted by an off-site mail facility on Tuesday.
Senate Majority Leader Harry Reid said he was told the letter was addressed to the office of Sen. Roger Wicker, R-Mississippi. After the envelope tested positive in a first routine test, it was retested two more times, each time coming up positive, the law enforcement source said. The package was then sent to a Maryland lab for further testing.Senators were briefed on the matter Tuesday evening and told the congressional post offices would be temporarily shut down."It was caught in the screening facility. That's why we have an off-site screening facility for mail," said Sen. Claire McCaskill, D-Missouri.Ricin is a highly toxic substance derived from castor beans. As little as 500 micrograms -- an amount the size of the head of a pin -- can kill an adult. There is no specific test for exposure and no antidote once exposed.
CDC page "Facts about Ricin" can be found here.