A second letter that tested positive for ricin addressed to President Barack Obama was discovered in an offsite mail screening facility, according to a statement released today by the FBI.
The envelope was quarantined and an investigation with the FBI initiated, they wrote, but operations at the White House haven't been affected.
Mail from a second government mail screening facility is being tested today as some preliminarily tested positive for ricin this morning, as well.
The FBI says field tests are conducted whenever a suspicious powder is located in a mail facility, but the results can be inconsistent. Whenever they come up positive, the material is then sent to an accredited lab to test for biological agents, like ricin. The tests are being conducted, and normally take between 24 and 48 hours to complete.
The investigation remains ongoing, and the FBI says more letters could be received.
They say there is no indication of a connection to the Boston attack on Monday.