TULSA - A letter addressed to President Barack Obama tested positive for the notorious poison ricin Wednesday, just a day after another letter containing the deadly substance was intercepted before it reached a senator.
The letter to Obama was found at an off-site White House mail facility Tuesday, and the Secret Service confirmed the presence of ricin, adding that further tests would be conducted.
It was "very similar" to a letter sent to Mississippi Sen. Roger Wicker, a Republican.
Tests are also being conducted on two other letters sent to lawmakers.
The Wicker letter was reportedly postmarked in Memphis, Tennessee.
Ricin is an extremely toxic substance, with no known cure.
It is made from castor beans, and can kill in as little as 36 hours.
Ground castor beans can test positive for ricin without actually being toxic.
KRMG received this statement from the Federal Bureau of Investigation:
A second letter containing a granular substance that preliminarily tested positive for ricin was received at an offsite mail screening facility. The envelope, addressed to the President, was immediately quarantined by U.S. Secret Service personnel, and a coordinated investigation with the FBI was initiated. 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.
Any time suspicious powder is located in a mail facility, field tests are conducted. The field and other preliminary tests can produce inconsistent results. Any time field tests indicate the possibility of a biological agent, the material is sent to an accredited laboratory for further analysis. Only a full analysis performed at an accredited laboratory can determine the presence of a biological agent such as ricin. Those tests are currently being conducted and generally take 24 to 48 hours.
The investigation into these letters remains ongoing, and more letters may still be received. There is no indication of a connection to the attack in Boston.