The U.S. Secret Service said Wednesday it's investigating a letter containing a "suspicious substance" that was addressed to President Obama, and said at least three U.S. senators have also reported receiving suspicious mail.
Te letter field-tested positive for the poison ricin and was received at the remote White House mail screening facility Tuesday, law enforcement officials said, according to the Associated Press.
The facility routinely identifies letters or parcels that require secondary screening or scientific testing before delivery. The Secret Service is working closely with the U.S. Capitol Police and the FBI in this investigation.
"The investigation into these letters remains ongoing, and more letters may still be received," the FBI said in a statement Wednesday morning. "There is no indication of a connection to the attack in Boston."
"It is important to note that operations at the White House have not been affected as a result of the investigation. Additionally, filters at a second government mail screening facility preliminarily tested positive for ricin this morning. Mail from that facility is being tested," the FBI added.
The suspicious letter send to President Obama comes on the heels of U.S. Capitol Police confirming it was investigating a letter addressed to Sen. Roger Wicker, R-Miss., that tested positive for the poison ricin in a preliminary examination.
Another suspicious package was received Wednesday morning at the Washington offices of Sen. Richard Shelby, R-Ala., according to the report. It was not known if it was similar to the ones addressed to Obama and Wicker.
Sen. Carl Levin, D-Mich., issued a statement saying that a suspicious letter also was received Wednesday morning at his Saginaw, Mich., field office. He said the staffer who received the letter did not open it and turned it over to authorities, who are investigating.
