All four workers worked at a facility that processed the letter that eventually wound up in the office of Senate Majority Leader Tom Daschle.

CNN: Postal workers angry over response

Barclays has also agreed to provide a letter of credit facility.

FORBES: Magazine Article

But members of the New York Police Department emergency service unit who came in contact with the letter that was opened at a city mail facility were examined for "minor symptoms" of ricin exposure that they experienced on Saturday, according to Paul Browne, NYPD spokesman.

WSJ: Letters to Mayor Bloomberg Tested Positive for Ricin

That letter was opened at the city government's mail facility, in a biochemical containment box.

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It was unclear precisely how the letter, which was intercepted Wednesday by the White House facility, was similar to letters laced with the poison ricin and addressed to Bloomberg.

NPR: Secret Service: Letter To White House Intercepted

According to the letter, the four-story building will be a research facility that will not replace the existing campus on 1 Infinite Loop.

CNN: Doug Gross,

Asked about Florida Attorney General Bill McCollum's Friday letter to Feinberg criticizing the claims process under the Gulf Coast Claims Facility, Feinberg again emphasized that the program is voluntary.

CNN: STORY HIGHLIGHTS

The letter addressed to Wicker and bearing no return address was intercepted by the U.S. Senate Mail Facility in Landover, Maryland, and the FBI was alerted of it Tuesday, the affidavit says.

CNN: FBI confirms letters to Obama, others contained ricin