MSNBC is now reporting that Carl Levin's regional office has also received a suspicious letter.
MSNBC is also reporting that they believe the letters are being sent from Mississippi and that federal officials believe they know who sent them, but there have been no arrests. The FBI does not think they are connected to the Boston explosions.
An envelope addressed to President Obama and intercepted at a mail processing facility has tested positive for the poison ricin, a law enforcement official said Wednesday.
Officials are conducting additional tests to confirm the result, said the official, who was not authorized to speak to the press because the tests are part of an ongoing investigation. Investigators believe the letter to the White House may have been sent by the same person who mailed a suspicious envelope to Sen. Roger Wicker (R-Miss.). [...]
All White House mail is processed at a remote facility not located at the White House complex. It is common for letters to be flagged and tested for suspicious substances, officials said.
WASHINGTON, D.C. (WAAY) - Spokesperson Johnathan Graffeo confirms a suspicious package has been located at the Washington, D.C. office of Senator Richard Shelby.