Oct. 2 (UPI) -- Two letters addressed to Defense Secretary James Mattis and another military official tested positive for the toxin ricin at a Pentagon mail sorting facility, the U.S. Defense Department said Tuesday.
A Pentagon spokesman said tests for two suspicious letters addressed to Defense Secretary James Mattis and John Richardson, chief of naval operations, were positive for ricin.
"The Pentagon Force Protection Agency detected a suspicious substance during mail screening at the Pentagon's remote screening facility," spokesman Col. Rob Manning said.
The department said the letters did not enter the Pentagon building, but rather the mail sorting facility on the Pentagon campus but away from the main building.
Officials said all incoming mail to the facility was being quarantined.
One official said the positive result came from a field test, which sometimes give false positives, NBC News reported.
Ricin is extracted from castor beans and can be used in a powder, pellet, mist or acid form. If ingested, it can cause nausea, internal bleeding of the stomach and intestines and ultimately organ failure. Ricin has for years been mentioned as a potential bio-terror attack method.
In June, a Wisconsin woman was accused of spreading Islamic propaganda online, including showing how to make ricin and deploy it at government facilities and water reservoirs. That same month, a ricin attack was foiled in Germany.