The latest on this was just reported on Fox News moments ago. Both letters reportedly were postmarked from Memphis, TN.
"An FBI bulletin obtained by Fox News also said a second letter was sent to Obama, and was intercepted. That letter is still being screened," Fox News reports.
The bulletin said both letters included the phrase: "To see a wrong and not expose it, is to become a silent partner to its continuance."
Both were signed, "I am KC and I approve this message."