In a seven-year-old secret program at the National Archives, intelligence agencies have been removing from public access thousands of historical documents that were available for years, including some already published by the State Department and others photocopied years ago by private historians.

Among the 50 withdrawn documents that Mr. Aid found in his own files is a 1948 memorandum on a C.I.A. scheme to float balloons over countries behind the Iron Curtain and drop propaganda leaflets. It was reclassified in 2001 even though it had been published by the State Department in 1996.

Another historian, William Burr, found a dozen documents he had copied years ago whose reclassification he considers "silly," including a 1962 telegram from George F. Kennan, then ambassador to Yugoslavia, containing an English translation of a Belgrade newspaper article on China's nuclear weapons program.

The program's critics do not question the notion that wrongly declassified material should be withdrawn. Mr. Aid said he had been dismayed to see "scary" documents in open files at the National Archives, including detailed instructions on the use of high explosives.

But the historians say the program is removing material that can do no conceivable harm to national security. They say it is part of a marked trend toward greater secrecy under the Bush administration, which has increased the pace of classifying documents, slowed declassification and discouraged the release of some material under the Freedom of Information Act.

According to this article, sometime today, researchers will be posting some of the discovered re-classified documents on GWU's National Archive page.