Second ricin-laced letter found in D.C.?

The Hill is reporting that a second letter, possibly ricin-laced and this time addressed to President Barack Obama, has been discovered in a D.C.-area mail facility:

Authorities have intercepted a letter to the White House that tested positive for ricin poison, according to multiple media reports.

The Secret Service has acknowledged the letter addressed to President Obama contained a suspicious substance but has not stated it was ricin, a deadly poison.

On Tuesday it was announced that a letter containing ricin was discovered in mail addressed to Republican Senator Roger Wicker of Mississippi.

More details are at The Hill.