A letter addressed to a U.S. senator from Mississippi has tested positive for the dangerous poison ricin, the FBI said Tuesday.
Senate Majority Leader Harry Reid said Tuesday evening that the toxin was sent to the office of Sen. Roger Wicker (R-Miss.) in an envelope postmarked Memphis, Tenn.
The tainted letter was intercepted and never made it to the Capitol, but mail to Senate offices was suspended as a result.
"This matter is part of an ongoing investigation by the United States Capitol Police and FBI. I want to thank our law enforcement officials for their hard work and diligence in keeping those of us who work in the Capitol complex safe," Wicker said in a statement Tuesday night.
The letter to Wicker was intercepted at the Landover, Md. mail facility. Wicker's office told his close associates that no one at the post office was exposed to the substance, a source close to him told NBC News.
The FBI field office in Baltimore said the first test in the field was preliminary, and afterward, a second test done in a lab also came back positive for ricin.
The Senate's top security official, the Sergeant at Arms, told NBC News that the appearance of the ricin-tainted letter "wouldn't raise suspicion."
"The bottom line is, the process we have in place worked," Sen. Claire McCaskill (D-Mo.) said Tuesday, just after senators were briefed on the letter.
She said officials have identified a person of interest — someone who "writes to a lot of members" of the Senate.
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