The United States Postal Service is being credited for detecting the ricin on the envelopes addressed to the President and Republican U.S. Senator from Mississippi, Roger Wicker.
News 5 talked by phone with a spokesman for the United State Postal Service, David Walton.
He tells us, each piece of mail they receive goes through a bio-hazard detection system.
"We take it seriously. So, that's why we have these processes and procedures in place to give us an advance warning if a piece of mail is contaminated," Walton tells us.
We went to Anderson Compounding Pharmacy in Bristol, Tennessee to find out exactly what ricin is.
"This has been around a long time. It's not anything that's been recently new development of any kind," says Women's Health Clinical Pharmacist, Beth Jenks.
Castor beans are processed to make castor oil, and ricin is part of the waste "mash" that's produced when castor oil is made.
"In that, they can extract the toxins out, using the ricin to make basically poisonous material," Jenks says.
However, while ricin could be fatal, we're told it causes far more scares than deaths.
According to the 2010 Homeland Security Department Handbook, the only recorded death from ricin happened in 1978.
Tennessee Congressman Phil Roe, who's in Washington right now, weighed in by phone Wednesday afternoon.
He says says we cannot let these recent acts of terror prevent us from living our everyday lives.
"Look at what happened in Boston, all those innocent people who were injured and unfortunately three deaths. Here, an attack with ricin, and we can't let terrorists intimidate us," Congressman Roe says.
We're told you either have to inhale, ingest, or be injected with ricin, for it to be harmful to you.
But authorities are not taking the recent scare lightly and postal workers are remaining vigilant.
Ricin is categorized as a 'Class B' threat, which is the agency's second-highest threat level, ranking behind things such as anthrax, smallpox, and the plague.