Before news came out about the second letter, Sen. Claire McCaskill (D) of Missouri told The Associated Press that the police have one suspect in mind. A person who “writes a lot of letters to members” of Congress is a suspect in the investigation, she said after emerging from a classified briefing.
US Capitol Police (USCP) and the Federal Bureau of Investigation would not comment on a potential suspect.
The letter addressed to Senator Wicker was intercepted at a Senate mail facility in Prince George’s County, Md., outside Washington. Police were notified that the mail center received “an envelope containing a white granular substance,” said Capitol Police spokesman Shennell S. Antrobus.
“The envelope was immediately quarantined by the facility's personnel, and USCP hazmat responded to the scene,” Mr. Antrobus said. “Preliminary tests indicate the substance found was ricin. The material is being forwarded to an accredited laboratory for further analysis.”
The interception of the letters appears to demonstrate the effectiveness of mail security protocols put into place after the anthrax mail attacks in 2001. During those attacks, five Americans died and 17 others became ill. Two Senate office buildings were closed after anthrax-laced letters reached the offices of then-Sen. Tom Daschle (D) of South Dakota, who was serving as majority leader, and Sen. Patrick Leahy (D) of Vermont. An investigation of the attacks concluded that Dr. Bruce Ivins, a government scientist who committed suicide in 2008, planned and executed the attacks alone.
Since then, officials have implemented major changes in how mail is handled for elected officials. Off-site facilities now handle mail addressed to members of Congress, as well as the president, and these facilities follow various screening and inspection procedures.
Still, in 2004, ricin was discovered in then-Senate majority leader Bill Frist's mailroom, and three Senate office buildings were closed.
But in the case of the letter addressed to Wicker, operations at the Capitol complex were not affected, Capitol Police said.
“Luckily, this was discovered at the processing center off premises,” Sen. Richard Durbin (D) of Illinois told AP. Mail addressed to senators is “roasted, toasted, sliced, and opened” before it ever gets to them, he said.
While the Capitol Police said the results indicated the substance is ricin, FBI spokesman Paul Bresson said that the initial tests produced mixed results, and further laboratory analysis would be needed to determine the exact substance.
“I have confidence in our procedures, our personnel, the United States Capitol Police response personnel, the strength and weaknesses of field testing and the need for laboratory confirmation,” Mr. Gainer said in an e-mail to The Washington Post.
There is no known antidote for ricin, which is a poison found naturally in castor beans, according to the Centers for Disease Control and Prevention. Ricin can be made from the material left over when processing castor beans for oil. The poison can take the form of powder, mist, or a pellet, and it can also be dissolved in water. Inhalation is considered the most dangerous mode of exposure.
Postal Service spokeswoman Patricia Licata would not say whether any employee had been exposed to the toxic substance found in the letter, but she said the agency is working with health and law enforcement officials.
“Our primary concern right now is the safety of our employees, the safety of our customers, and the safety of the US mail,” Ms. Licata said.
Wicker was appointed to the Senate in 2007 after serving almost 13 years in the House, and he was reelected last year. He issued a brief statement in response to the letter addressed to him, saying that the investigation is ongoing.
“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,” he said.
• Material from The Associated Press contributed to this report.