Federal officials discovered Tuesday a poison-laced letter sent to Sen. Roger Wicker (R-Miss.), uncovering the material at an off-site location where congressional mail has been screened since anthrax-laced letters were sent to Capitol Hill in 2001.

Senate Majority Leader Harry M. Reid (D-Nev.) and other senators exiting an FBI briefing on the Boston attacks, told reporters that the letter was tested at the facility and came up positive for ricin. Officials gave no indication why the letter was sent to Wicker, a low-profile senator in his second term.