An envelope containing ricin was sent to the Capitol Hill office of Sen. Roger Wicker, lawmakers told Fox News on Tuesday.
Ricin, a potentially lethal poison, is derived from the same bean that makes castor oil. According to a Homeland Security Department handbook, ricin is deadliest when inhaled. It is not contagious, but there is no antidote.
"Luckily, this was discovered at the processing center off premises," Sen. Dick Durbin, D-Ill, said. He said all mail to senators is "roasted, toasted, sliced and opened" before it ever gets to them.
One law enforcement official said evidence of ricin appeared on preliminary field tests of the letter, although such results are not deemed conclusive without further testing. The official spoke on condition of anonymity because the investigation remains active.
Ricin prevents the cells of a person’s body from making the proteins they need, according to the Centers for Disease Control and Prevention.
Without the proteins, the cells die eventually becoming harmful to the whole body and possibly leading to death.
Symptoms of ricin poisoning depend on a person’s exposure to it.
If a significant amount of ricin is inhaled, the likely symptoms would be difficulty breathing, fever, cough, nausea, and tightness in the chest, according to the CDC. Low blood pressure and respiratory failure may occur leading to death.
If ricin is swallowed, a significant amount of ricin, he or she would likely develop vomiting and diarrhea that may become bloody. Severe dehydration may be the result, followed by low blood pressure. Other signs or symptoms may include seizures, and blood in the urine, according to the CDC. Within several days, the person’s liver, spleen, and kidneys might stop working, leading to death.
If a person’s skin makes contact with ricin powders or products, redness and pain of the skin and eyes may occur, the CDC reports.
The discovery evoked memories of the days after the terrorist attacks of Sept. 11, 2001, when mail laced with anthrax began appearing in post offices, newsrooms and congressional offices.
That included letters sent to Sen. Tom Daschle, D-S.D., who was Senate majority leader, and Sen. Patrick Leahy, D-Vt. Two Senate office buildings were closed during that investigation.
Overall, five people died and 17 others became ill. The FBI attributed the attack to a government scientist who committed suicide in 2008.
More immediately, though, the discovery came as lawmakers were demanding answers to the attacks in Boston a day earlier.
There was no evidence of a connection between the bombings and the letter addressed to Wicker.
The Associated Press contributed to this report.