The two suspicious envelopes were addressed to Secretary of Defense James Mattis and to Chief of Naval Operations, Admiral John Richardson, the official told CNN.

The mail facility is in a separate building on the grounds of the Pentagon and the piece of mail which tested positive never entered the Pentagon building.

All US Postal Service mail received at the Pentagon mail screening facility on Monday is currently under quarantine and poses no threat to Pentagon personnel, according to Pentagon spokesperson Col. Rob Manning.