WASHINGTON A letter addressed to the office of Sen. Roger Wicker, R-Miss., contained a suspicious substance that might be potentially deadly ricin, sparking new fears of security threats in Congress at the same time the country was reeling from the bomb attacks in Boston.
The letter, discovered at a mail facility in Landover, Md., just outside Washington, was field-tested positive for ricin, according to an FBI official who spoke on condition of anonymity in order to discuss the inquiry. While cause for alarm, that test was not conclusive, the official said.
Another law enforcement official familiar with the investigation said that the letter contained both a threatening letter and a powder. Four tests were done in all: Two were positive for ricin, and two were negative, he said.
The official, who asked not to be identified because he was not authorized to discuss the investigation, said the conflicting tests suggested that the powder might not be poison. Additional tests are being done.
The postal facility where the congressional mail is inspected, he said, was having a problem with tests that erroneously show substances as poisonous. "The facility is famous for false positives," he said.
The official also said investigators have found no link between the letter to Wicker and the bombings in Boston.
Officials said the letter was postmarked in Memphis, Tenn., and sent to the Washington office of the Mississippi Republican. It was sent first to a special testing facility far from the U.S. Capitol and never made it to the senator's office.
"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 evening.
News of the contaminated letter, coming a day after the explosions at the Boston Marathon that killed three, shook the Capitol. Senators were briefed by FBI and Homeland Security officials about the letter at an early evening session called to inform them about the Boston explosions.
Sen. Claire McCaskill of Missouri said authorities have a suspect, but she did not say if an arrest had been made, the Associated Press reported. She added the letter was from an individual who frequently writes lawmakers, the AP said.
Capitol Police, the FBI and other agencies were investigating. There was "no indication that there are other suspect mailings," according to Senate Sergeant at Arms Terrance Gainer.
Gainer said "exterior markings on the envelope in this case were not outwardly suspicious, but it was postmarked from Memphis, Tenn., and had no return address."