The FBI said there is no connection between Monday's Boston Marathon bombing and two ricin-tainted letters mailed from Memphis to President Barack Obama U.S. Sen. Roger Wicker (R-MS).
The president's tainted letter was received Tuesday at a mail screening facility near the White House and Sen. Wicker's tainted letter was intercepted at the Congressional Mail Sorting Office in Prince Georges County in Maryland.
Both letters were tested positively for ricin and were postmarked in Memphis April 8 with no return address.
FBI agents in Memphis are involved in this investigation, but multiple agencies are working this case. The Memphis mail center is part of a federal investigation.
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White House Press Secretary Jay Carney confirmed a letter was addressed to the president.
"There was a letter sent to addressed to the president, at an off-site mail facility, that was noticed to contain a suspicious substance and tests were undertaken," Carney said.
Officials say the two letters have the same signature that reads, "I am KC and I approve this message."
An FBI bulletin obtained by the Associated Press said the text of the letters read, "to see a wrong and not expose it, is to become a silent partner to its continuance."
The first letter was intercepted at a Congressional mail sorting facility in Maryland Tuesday and it was bound for Sen. Wicker's Capitol Hill office.
"This matter is part of an ongoing investigation by the United States Capitol Police and FBI," Sen. Wicker said in a statement Tuesday evening. "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."
Reports of the poison letters put Capitol Hill on edge. Two Congressional office buildings were partially evacuated Wednesday as Capitol Police investigated reports of suspicious activity. An all clear was given later.
In the Mid-South it looked like a regular day at the post office, but Mid-South Homeland Security officials are prepared to deal with ricin and they warn it is a deadly poison.
An FBI official told FOX13 News they have two priorities. They are testing the letters to find out if this really is ricin, as sometimes the initial field tests are wrong. They are also looking for the person who sent the two tainted letters intended for the president and Sen. Wicker.