A preliminary investigation has shown that the mysterious substance found on envelopes addressed to Defense Secretary James Mattis and Chief of Naval Operations John Richardson is castor seeds, The Hill reported Wednesday.
Defense Department spokesperson Dana White revealed the results of the initial analysis to The Hill via a statement, noting, however, that the FBI is still conducting further tests.
The Pentagon Force Protection Agency detected the suspicious substance while screening mail at a remote facility on Monday. The Wall Street Journal reports that the envelopes tested positive for the poison ricin following an on-site test.
Ricin can be produced using castor seeds, but the seeds on their own would only be dangerous if swallowed.