WASHINGTON - An envelope addressed to Sen. Roger Wicker of Mississippi twice tested positive Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three and left more than 170 injured at the Boston Marathon.
One senator, Claire McCaskill of Missouri, said authorities have a suspect in the fast-moving ricin case, but she did not say if an arrest had been made. She added the letter was from an individual who frequently writes lawmakers.
On Tuesday night, FBI spokesman Paul Bresson said initial field tests on the substance produced mixed results and that it is in the process of undergoing further analysis at an accredited laboratory. Only after that testing can a determination be made about whether the substance is ricin, Bresson said.
A U.S. Capitol Police officer walks past Sen. Roger Wicker, R-Miss., office in the Dirksen Senate Office Building on Capitol Hill in Washington, Tuesday. An envelope addressed to Wicker tested positive Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three and left more than 170 injured at the Boston Marathon.
The U.S. Capitol Police, which is also investigating the case, declined to comment.
Late Tuesday, Wicker released a statement acknowledging the letter and said it was sent to his Washington office.
"This matter is part of an ongoing investigation by the United States Capitol Police and FBI," Wicker said. "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."
Terrance W. Gainer, the Senate sergeant-at-arms, said in an emailed message to Senate offices that the envelope to Wicker, a Republican, had no obviously suspicious outside markings and lacked a return address. It bore a postmark from Memphis, Tenn.
Mail from a broad swath of northern Mississippi, including the Memphis suburbs of DeSoto County, Miss., Tupelo, Oxford and the northern part of the Mississippi Delta region is processed and postmarked in Memphis, according to a Postal Service map. The Memphis center also processes mail for residents of western parts of Tennessee and eastern Arkansas.
Gainer said there was "no indication that there are other suspect mailings." Yet he urged caution, and also said the Senate off-site mail facility where the initial tests were performed on the letter will be closed for a few days while the investigation continues.
The letter was discovered at a mail processing plant in Prince George's County in suburban Maryland, according to Sen. Dick Durbin, D-Ill.
Wicker, 61, was appointed to the Senate in 2007 and won election to a full term two years ago. He previously served a dozen years in the House.