(RNN) - The FBI confirms that an preliminary test of an envelope sent to President Barack Obama contained ricin. The news comes one day after a letter containing ricin was intercepted en route the office of Sen. Roger Wicker, R-MS.
Both letters are confirmed to have been postmarked in Memphis.
Although preliminary testing on the letters at off-site mail facilities yielded positive results, The FBI said will conduct further testing. The FBI also states the letters have no bearing to the attack in Boston.
Field tests are conducted at the off-site mail facilities and results are often inconsistent. Those tests results can take 24 to 48 hours.
Concern shifts to the postal workers sorting the mail and if they were exposed to ricin. During the anthrax scare after September 11, two postal workers died after exposure to the poison.
According to the Associated Press, the FBI said the letters sent to Obama and Wicker are related and were both postmarked on April 8. Both letters contain, "To see a wrong and not expose it, is to become a silent partner to its continuance," and are signed, "I am KC and I approve this message."
The lockdown of two U.S. Senate buildings - Hart and Russell - have been lifted after the bomb squad swept the buildings.
Across the country, Sen. Carl Levin's Saginaw, MI office has been evacuated due to a suspicious letter. Hazmat crews are on the scene.
Levin, who is chairman of the Senate Armed Services Committee, is not in the office.
Reports state that investigators are also looking into a suspicious envelope or package at the office of Sen. Richard Shelby, R-AL.
CNN reports police have a man in custody who was carrying a backpack filled with sealed envelopes. These envelopes did not set off any metal detectors, according to CNN, and was therefore allowed into the Hart Building.
Various senate offices accepted the sealed letters, which does not follow protocol, and police are testing the envelopes and offices.
The letters to Obama and Wicker came in Tuesday to separate mail processing facilities.
According to CNN, a law enforcement official described the letter as, "very similar" to the one sent to Wicker on Tuesday, but would not comment if the similarities were in appearance, type of paper or what the letter said.
"The last few days have been trying ones for our nation. Monday's attack in Boston reminded us that terrorism can still strike anywhere at any time. And as yesterday's news of an attempt to send ricin to the Capitol reminds us it is as important as ever to take the steps necessary to protect Americans from those who would do us harm," Sen. Mitch McConnell said.
The FBI said there is no indication of a connection to the attacks in Boston.
The substance from the letters have been sent to a laboratory at Fort Detrick in Frederick, MD, where both the U.S. Army Medical Research and Materiel Command and the U.S. Army Medical Research Institute of Infectious Diseases are located.
Police have a suspect in mind as they investigate the suspicious envelope that was sent to Wicker, according to the Associated Press.
"It was caught in the screening facility. That's why we have an off-site screening facility for mail," said Sen. Claire McCaskill, D-MO, to CNN on Tuesday.
The envelope tested positive in a routine test, and in two other subsequent tests, law enforcement officials tell CNN.
McCaskill told Politico the letter came from a person who writes to lawmakers, but declined to identify the individual.
The Associated Press reports lawmakers were informed of the incident in a closed-door meeting about the Boston Marathon bombings.
CNN reports Wicker now has a protective detail.
Wicker issued a statement Tuesday saying "This matter is part of an ongoing investigation by the United States Capitol Police and FBI. 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 also thanked everyone for their thoughts and prayers.
Ricin is extremely poisonous and is made from castor beans. According the New York Department of Health, accidental exposure to ricin is "highly unlikely."
No antidote exists for ricin poisoning and death could take from 36 to 72 hours after exposure. Ricin can be in the form powder, a mist or a pellet and can be dissolved in liquid.
Symptoms, which can present 4 to 6 hours after exposure, include respiratory distress (difficulty breathing), fever, cough, nausea, and tightness in the chest. Heavy sweating may follow as well as fluid building up in the lungs," according to the Center for Disease Control and Prevention.
The incident is reminiscent of the anthrax scare after September 11 where five people died and 17 others were exposed. Envelopes were sent to congress and NBC News containing anthrax. However, the letters were not related to 9/11.
However, those letters were received a week after the attacks; these letters were received one day after the bombing in Boston.
How mail was processed and sent to congress was changed as a result.
Ricin has been used in other countries in assassinations, such as the poisoning of Georgi Markov, a Bulgarian dissident, in 1978. He was jabbed by the tip of an umbrella in London and died four days later.
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