The Defense Department, stung by months of criticism from sick Persian Gulf War veterans, decided to declassify thousands of pages of documents from the 1991 conflict to prove it has nothing to hide. At the same time, Pentagon scientists concluded that they, like others before them, could not confirm any single cause for the mysterious, flu-like illnesses that have afflicted thousands of troops. The researchers say the varied symptoms reported by soldiers could not be traced to Iraqi biological or chemical weapons. Medical testing, however, will continue. TIME defense correspondent Mark Thompson says many vets still believe there's a U.S. cover-up going on, but he strongly doubts it: "If the Pentagon were able to say, 'We believe Saddam Hussein did this,' they would be eager to do that."