(CNN) — An envelope that tested positive for the deadly poison ricin was intercepted Tuesday afternoon at the U.S. Capitol's off-site mail facility in Washington, congressional and law enforcement sources tell CNN.
Senate Majority Leader Harry Reid said he was told the letter was addressed to the office of Sen. Roger Wicker, R-Mississippi. A laboratory in Maryland confirmed the presence of ricin after initial field tests indicated the poison was present, Senate Sergeant-at-Arms Terrance Gainer said.
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The letter had a Memphis, Tennessee, postmark and no return address, Gainer wrote in an e-mail to senators and aides. In a statement late Tuesday, the U.S. Capitol Police said more tests would be conducted at the Army's biomedical research laboratory at Fort Detrick, Maryland.