An envelope addressed to a Republican senator tested positive on Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three people and left more than 170 injured at the Boston Marathon.
Senator Claire McCaskill said authorities have a suspect in the fast-moving ricin case, but she did not say if an arrest had been made. She added that the letter was sent from an individual who frequently writes to lawmakers.
Late on Tuesday, Senator Roger Wicker of Mississippi 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.”
Shennell Antrobus, a spokesman for the US Capitol Police (USCP), said on Tuesday night that the Capitol Police had been notified by the Senate mail handling facility that “it had received an envelope containing a white granular substance.”
“The envelope was immediately quarantined by the facility’s personnel and USCP HAZMAT [hazardous materials] responded to the scene,” Antrobus said. “Preliminary tests indicate the substance found was ricin. The material is being forwarded to an accredited laboratory for further analysis.”
FBI spokesman Paul Bresson said earlier that 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.
Senate sergeant-at-arms Terrance Gainer said in an e-mailed message to Senate offices that the envelope to Wicker had no suspicious outside markings and lacked a return address. It bore a postmark from Memphis, Tennessee.
Mail from a broad swath of northern Mississippi, including the Memphis suburbs of DeSoto County, Mississippi, Tupelo, Oxford and the northern part of the Mississippi Delta region, is processed and postmarked in Memphis, according to a US Postal Service map.
The letter was discovered at a mail processing plant in Prince George’s County in suburban Maryland, according to Senator Dick Durbin, the No. 2 Senate Democrat.
Wicker, 61, was appointed to the Senate in 2007 and won election to a full term last year. He previously served a dozen years in the House of Representatives.
He has a solidly conservative voting record, so much so that he drew notice last week when he voted to allow debate to begin on controversial gun legislation in the Senate.
Majority Leader Harry Reid told reporters of the letter.
Other lawmakers said they had been provided information by Gainer’s office.
Milt Leitenberg, a University of Maryland bioterrorism expert, said ricin is a poison derived from the same bean that makes castor oil. According to a Homeland Security Department handbook, ricin is deadliest when inhaled. It is not contagious, but there is no antidote.
“Luckily, this was discovered at the processing center off premises,” Durbin said. He said all mail to senators is “roasted, toasted, sliced and opened” before it ever gets to them.
A congressional official said evidence of ricin appeared on two preliminary field tests of the letter, although such results are not deemed conclusive without further testing. The official spoke on condition of anonymity because the investigation remains active.