It was not immediately clear when the envelope was received. Letter with ricin sent to Wicker

An envelope sent to the Washington, D.C., office of Sen. Roger Wicker (R-Miss.) included a substance that has tested positive for the toxic substance ricin.

The Senate mail facility on Tuesday notified the U.S. Capitol Police that it had received an envelope containing “a white granular substance,” according to a release. The envelope “was immediately quarantined” at the off-site facility, and Capitol Police hazardous material personnel responded.


“Preliminary tests indicate the substance found was Ricin,” said the police statement, which was released late Tuesday night. “The material is being forwarded to an accredited laboratory for further analysis.”

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The Capitol Police says it is partnering with the FBI for an “ongoing investigation.” The statement added that the Capitol complex has not been affected.

The U.S. Senate mail facility is currently closed for more testing — all mail bound for Capitol Hill is now being directed through a U.S. House facility.

The letter was postmarked Memphis, Tenn., and had no suspicious markings or return address, according to a message sent to congressional staffers by Senate Sergeant at Arms Terrance Gainer. Gainer indicated that the Senate mail facility would be closed for two to three days “while testing and the law enforcement investigation continues.”

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Sen. Claire McCaskill (D-Mo.) said members were briefed that the substance had been found in a letter and that a suspect has been identified.

McCaskill said the letter came from an individual who frequently writes to lawmakers. She wouldn’t identify the person but confirmed officials were investigating someone.

McCaskill said state offices have been told what to look for if there are more letters containing the toxic substance.

( Also on POLITICO: What is ricin?)

The Senate went into recess shortly after 6 p.m. Homeland Security Secretary Janet Napolitano and FBI Director Robert Mueller began briefing senators shortly afterward about the incident. A Homeland Security official said that the briefing was intended to address cybersecurity but that the subject pivoted after the ricin substance was discovered.

All congressional mail is screened ever since Capitol Hill-bound letters laced with anthrax were discovered in October 2001, which contributed to the death of five people and infected 17 more. Senate offices were closed for several days in 2004 when ricin was found in the offices of then-Senate Majority Leader Bill Frist (R-Tenn.).

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The incident comes one day after three people were killed and 176 were injured as two bombs exploded at the Boston Marathon. The FBI is investigating the Boston bombings as an “act of terrorism,” though whether domestic or international is unclear. President Barack Obama will travel to Boston on Wednesday. Lawmakers reacted to the unfortunate timing.

“I don’t know if that’s coincidence,” said Senate Majority Whip Dick Durbin (D-Ill.) said of the timing. “It’s too early to tell. We don’t know enough about Boston to even speculate.”

Napolitano ignored questions from reporters as she left the briefing. The FBI had no comment on the matter, and the Secret Service said it’s not involved in any investigation. “Metro Transit Police are aware of the ongoing investigation on Capitol Hill and are monitoring developments,” said a spokesman for the District of Columbia police force.

“This matter is part of an ongoing investigation by the United States Capitol Police and FBI,” Wicker said in a statement released on Tuesday night. “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. Gayle and I appreciate everyone’s thoughts and prayers.”

Michigan Sen. Carl Levin (D-Mich.) commended authorities for taking “real good precautions to notify everybody as to what happened. So what happened is far enough away and was caught in a way that did no damage that I’m not excessively concerned about it,” Levin said. “I think they’ve taken strong steps to avoid any problem.”

Levin said he didn’t think other senators were targets.

“Not that they gave us. I’m not sure [Wicker] was a target. You’re assuming he was a target — and I don’t know that. It wasn’t stated in that meeting.”

Senate Majority Leader Harry Reid (D-Nev.) confirmed the letter was sent to Wicker’s office and said that at that point, the incident appeared to be a solitary one.

In his letter, Gainer urged state Senate offices to use a device known as the Postal Sentry, which is offered free of charge to Senate offices, to scan mail for potentially harmful substances.

Ricin is a toxic substance made from castor beans. Ricin poisoning could cause symptoms such as respiratory distress, fever, cough, nausea, and tightness in the chest, as well as heavy sweating and chest tightness, according to the Centers for Disease Control and Prevention. There is no known antidote.

Manu Raju and Adam Snider contributed to this report.