The money had been flown by the Pentagon in planeloads of shrink-wrapped $100 bills in 2003 and 2004 but a failure to keep complete records showing how it was spent sparked concerns some or all of it had been stolen, the Los Angeles Times reported.
The audit, by the special inspector general for Iraq reconstruction, found "sufficient evidence exists showing almost all" the money was properly transferred to the Central Bank of Iraq.
But some of the cash still hasn't been accounted for, including $217 million that had been delivered to U.S. defense officials to be kept in a vault in a presidential palace in Baghdad, the audit found.
The $6.6 billion was part of $21 billion in Iraqi funds the U.S. Coalition Provision Authority had controlled when reconstruction began in the country after the U.S.-led invasion of Iraq. The money came from sales of Iraqi oil and other government assets and from an oil-for-food program administered by the United Nations that was imposed during Saddam Hussein's regime.
Iraqi officials had gone to the United Nations in the spring, claiming a "financial crime" and demanding restitution from the U.S. government.
Cash often had been given out with poor record-keeping as U.S.officials attempted to proceed quickly with rebuilding, the Times said.
Stuart Bowen, the inspector general, told the Times he would present his findings next month to a committee of top Iraqi officials in Baghdad who "have been eagerly awaiting our results."