WASHINGTON - The FBI says the letters sent to President Barack Obama and Sen. Roger Wicker are related and are both postmarked out of Memphis, Tenn., dated April 8.
In an intelligence bulletin obtained by The Associated Press, the FBI says the letters both say: "To see a wrong and not expose it, is to become a silent partner to its continuance." Both letters are signed, "I am KC and I approve this message."
The FBI says the substance in both letters have preliminarily tested positive for ricin, a potentially fatal poison.
Both the letters to Wicker, R-Miss., and to Obama were intercepted at off-site mail facilities.
The FBI says it is pursuing investigative leads to determine who sent the letters.
In another development, Michigan Sen. Carl Levin says his regional office in Saginaw received a suspicious letter and that authorities have been alerted.
Levin says in a statement that an aide received the letter Wednesday, but did not open it. Authorities are now investigating.
The Democratic lawmaker says he and his staff do not know if the mail presented a threat.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
The FBI says preliminary tests on a letter sent to President Barack Obama indicate the presence of poisonous ricin.
The letter is undergoing further testing because preliminary field tests can be unreliable, creating false positives.
The letter was intercepted at a facility away from the White House. It comes the day after officials said a letter sent to Sen. Roger Wicker tested positive for poisonous ricin. That letter to Wicker, a Republican, was intercepted at a Senate mail facility just outside Washington.
The FBI says there is no indication of a connection to the bombing at Monday's Boston Marathon.
In another late breaking development, Michican Senator Carl levin says his regional Saginaw office received a suspicious letter.
Tensions have been high in Washington and across the country since the deadly bombings on Monday at the Boston Marathon that killed three people and injured more than 170.