The stories we are publishing today are the result of a joint reporting project by ProPublica, the PBS program “FRONTLINE,” and McClatchy Newspapers.

The case of the anthrax letters has been unfolding for a decade now. Some of those involved in preparing these reports covered the story when it broke and had been investigating bio-defense issues even earlier.

Stephen Engelberg, ProPublica managing editor and a reporter on these stories, co-authored the book "Germs,'' a history of biological warfare that appeared in September 2001, only days before the first anthrax letters were mailed. The book drew on interviews with many in the bio-defense community, though not Bruce Ivins, the U.S. Army scientist ultimately accused of the mailings.

Gary Matsumoto, a contributor to ProPublica and a reporter on this project, has covered bio-defense for nearly 20 years. His Freedom of Information Act requests in the late 1990s about possible problems with a "second generation" anthrax vaccine irritated Ivins, one of the new vaccine's inventors. Matsumoto says he had cordial relations with Ivins, who figured prominently in his 2004 book, “Vaccine A.”

In 2003, Matsumoto also reported stories raising the possibility that the anthrax had been deliberately coated with chemicals to make it flow more efficiently. The FBI and its scientists have long denied this was the case.

Jim Gilmore has worked with "FRONTLINE" for more than 20 years reporting on national security stories, including films on the threat posed by bioterrorism and cyberwar. He was a producer of the 1998 film “Plague War,” which looked at the rise and fall of the Soviet Union’s vast secret biological weapons program.

Greg Gordon, a McClatchy investigative reporter, has written extensively about bio-terrorism and the anthrax letter attacks. He has spent 34 years covering the nation’s capital, including events such as the 9/11 attacks and the hunt for the Unabomber.

Mike Wiser, a FRONTLINE producer, has spent much of the last eight years investigating the American government's response to the 9/11 attacks. His most recent project, "Top Secret America," looked at the growth of government secrecy over the past decade.

The 10th anniversary of the Ivins case has been extensively covered in print and broadcast, including a report by CNN that included interviews with Los Angeles Times reporter David Willman, whose recent book “The Mirage Man” argues that Ivins harbored a dark side and had the means and motive to prepare the letters.

Two other recent books have revisted the case. “I Heard the Sirens Scream: How Americans Responded to the 9/11 and Anthrax Attacks,” is by Laurie Garrett; a Pulitzer Prize winning writer. And “American Anthrax: Fear, Crime, and the Investigation of the Nation's Deadliest Bioterror Attack," is by Jeanne Guillemin, a senior fellow in the Security Studies Program at Massachusetts Institute of Technology, in the Center for International Studies.