Treasury Inspector General Jeffrey Rush Jr. said the 140 of the 19,000 documents O'Neill requested and received after his dismissal were in fact classified, although O'Neill did nothing wrong, the New York Times said Tuesday.
Material from the documents formed the backbone of O'Neill's book that strongly criticized the Bush administration. In "The Price of Loyalty: George W. Bush, the White House and the Education of Paul O'Neill," writer Ron Suskind follows O'Neill's two years as Treasury Secretary and his dismissal as part of the Bush administration economic shake-up.
The inspector general's investigation said mislabeling had caused the release of the "national security or sensitive but unclassified" material.
O'Neill successor John Snow told Congress last month procedures were being changed to prevent future similar disclosures.
Notable deaths of 2014 [PHOTOS]