US authorities are investigating a letter addressed to President Barack Obama after the contents preliminarily tested positive for the deadly poison ricin, the second report of such a letter in two days. The FBI said the envelope was received at a mail screening facility outside the White House and was immediately quarantined. There was no indication of a connection to Monday's bomb attacks at the Boston Marathon, which killed three people and injured 176 others, the FBI said. Washington was put on edge Tuesday evening when news emerged that authorities had intercepted a letter sent to Republican Senator Roger Wicker of Mississippi that had initially tested positive for ricin. Then on Wednesday, a flurry of reports of suspicious letters and packages further rattled the US capital and caused the temporary evacuation of parts of two Senate buildings. Most of the reports, however, quickly proved to be false alarms, and business was only temporarily disrupted on Capitol Hill. The mailings to Obama and Wicker were related, based on the postmarks and the identical language of the enclosed letters, according to an FBI operations bulletin reviewed by Reuters. The letters included the phrase, "To see a wrong and not expose it, is to become a silent partner to its continuance," and were signed, "I am KC and I approve this message." The envelopes both bore postmarks from Memphis, Tennessee, and were dated April 8. Memphis Mayor A.C. Wharton pointed out in a statement, however, that this does not mean the letters originated in that city. An aide to Wharton explained that many areas near Memphis also are included in its postmark - including some in neighboring northern Mississippi, Wicker's state. For Washingtonians, the situation was unsettlingly reminiscent of events of nearly 12 years ago. Then letters containing anthrax spores were mailed to the Washington offices of two senators and to media outlets in New York and Florida, not long after the Sept. 11, 2001, attacks in New York and Washington.
