WASHINGTON — At least two items at the Pentagon's mail facility were suspected of containing ricin, a poison made from castor beans, a defense official said.

The mail was addressed to Secretary of Defense James Mattis and U.S. Navy Adm. John Richardson, chief of Naval Operations, another defense official said. Pentagon spokesman Christopher Sherwood confirmed that the items were addressed to individuals in the building but would not reveal their identity.

Mattis was traveling to Paris and Brussels, and not at the Pentagon.

The suspicious packages were caught during a mail screening at the Pentagon's remote screening facility, explained U.S. Army Col. Rob Manning, a Pentagon spokesman, in an emailed statement Monday adding that the FBI took the items for further analysis.

"All USPS mail received at the Pentagon mail screening facility yesterday is currently under quarantine and poses no threat to Pentagon personnel," Manning added.

The FBI confirmed its role alongside the Pentagon's Force Protection Agency but would provide no further comment.

Ricin is part of the waste "mash" produced when castor oil is made. According to the Centers for Disease Control and Prevention, if it is made into a partially purified material or refined, ricin can be used as a weapon capable of causing death under certain circumstances.

-The Associated Press contributed to this report.