According to CNN, two pieces of mail received by the Pentagon mail facility have tested positive for ricin. The mail arrived in the facility on Monday, according to US defense officials.
The mail facility is not inside the Pentagon building itself, but is on-campus. NBC News is reporting that the packages were addressed to someone in the Pentagon.
The FBI is investigating along with the Pentagon Force Protection Agency. All delivered mail was placed into quarantine until further notice.
Ricin is an extract of the castor bean and can be fatal if ingested. It's often used in terror plots and can be found in various forms such as powder, mist or acid.