Aerial view of the Pentagon. Photo: Bill Clark/CQ Roll Call
An initial test detected ricin on packages addressed to Defense Secretary James Mattis and Admiral John Richardson, the chief of naval operations, during a screening at the Pentagon's mail facility Monday, according to CNN.
The details: The remote mail facility is in a separate building on the Pentagon's grounds, and the envelopes that tested positive did not enter the Pentagon itself. Ricin is a poisonous substance found naturally in castor beans, according to the CDC. If ingested, the substance can cause fever, cough, difficulty breathing, nausea and tightness in the chest.