Someone may have tried to mail a letter laced with the deadly poison ricin to the office of Sen. Roger Wicker, R-Miss., but the envelope was intercepted at a mail facility outside Washington.

For now, Senate mail delivery has ceased as a precaution.

The United States Capitol Police say the letter was discovered Tuesday morning and that the envelope contained “a white granular substance” and was immediately quarantined by a HAZMAT team.

The letter is now being analyzed at a lab to determine if the substance is indeed ricin, police said. The FBI is also involved in the investigation.

“Postal officials and law enforcement did an excellent job in detecting and preventing this threat before it reached the Capitol,” said Don Stewart, spokesman for Senate Minority Leader Mitch McConnell, R-Ky. “The protective measures worked.”

Senators learned of the poisoned letter at a closed-door briefing Tuesday evening with Homeland Security Secretary Janet Napolitano and FBI Director Robert Mueller, who were briefing lawmakers about Monday’s bombing in Boston.

Those who were briefed on the incident said the letter had no return address and had a Memphis postmark.
According to the Centers for Disease Control, ricin is a poison derived from castor beans and can be ingested through food, air or water.

“It would take a deliberate act to make ricin and use it to poison people,” the CDC states on its website. “Unintentional exposure to ricin is highly unlikely, except through the ingestion of castor beans."

This is the second time ricin has been detected in Senate mail. When it happened in 2004, several Senate offices were closed until investigators determined that the ricin reading may have been false, triggered by the byproduct of castor beans plant used to produce the paper.

In 2001, anthrax-laden letters killed five people across the country and infected many others, including dozens of Capitol Hill staffers who opened spore-laden letters sent to several senators.

The anthrax attack prompted Capitol officials to alter the mail service, requiring that all letters be tested off site and many of them are now scanned and sent electronically rather than personally delivered to offices.

Wicker, the intended recipient of the latest ricin-contaminated letter, issued a statement Tuesday night.

“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. Gayle and I appreciate everyone’s thoughts and prayers.”