And we saw in the well-trained first responders, effective mail screening facilities and impressively swift law enforcement pursuit of wrongdoers that the investment we have made in preparation has paid off.

CNN: Not all terrorism is equal

Preliminary tests on filters at a government mail-screening facility also indicated the presence of ricin Wednesday morning, and mail from that site also was being tested, the FBI said.

CNN: Ricin scare rattles Washington

Officials have urged 2, 000 workers at the mail facility to undergo screening for the disease.

CNN: Neighbors mourn postal worker

Passengers may be thoroughly checked, but behind-the-scenes security is slack or non-existent, with inconsistent screening of mail, cargo and baggage, and an inadequate police presence, it said.

ECONOMIST: Canada

Thomas Veale confirmed that DIA discovered "possible biological toxins" that were "potentially harmful" on Tuesday morning during "routine screening" of its incoming mail.

WSJ: Ricin Charges Are Dropped

" Mr. Carney said the Secret Service and the White House were following their normal mail-processing procedures, which include screening letters and sending suspicious items to a remote location for "more intense testing.

WSJ: Man Is Arrested in Ricin Scare

The law-enforcement official said all of the mayor's mail is sorted and handled in several off-site facilities, and mail sent to the mayor's home goes through the same screening protocol.

WSJ: Letters to Mayor Bloomberg Tested Positive for Ricin