Washington (CNN) -- The U.S. official in charge of investigating fraud in Iraq said Monday he is carrying out a third audit to see if it might determine what happened to $6.7 billion in cash that was flown into Iraq eight years ago and is now missing.
"It has not been properly accounted for," said Stuart Bowen, special inspector general for Iraq reconstruction.
The money -- which belonged to Iraq -- was part of a sum of $20 billion that was shipped into war-torn Baghdad in bricks of hundred-dollar bills. They were shrink-wrapped and stored in the Central Bank of Iraq to pay for reconstruction.
"Our job as auditors is to find out how that was used, whether it was wasted or fraudulently misused, as we fulfill our mandate to get to a conclusory answer," he said.
Bowen blamed the system that existed then. "The system was too loose and unregulated in 2003 and 2004," he said. "Billions of dollars being flown into, effectively, a war zone; an insurgency exploding into a civil war; and fairly continuous turnover in government ministers and ministry personnel presented an atmosphere that some have described as Wild West-like and I think that's a fair description."
Bowen said he did not want to speculate on who the potential criminals might be, then added, "But this money was delivered to Iraqi control, and we have in the past had a number of cases reported to us about interim ministers who did steal."
During 2003 and 2004, he said, the money was under the aegis of the Coalition Provisional Authority, the entity created by the United States to govern Iraq after the fall of the regime of Saddam Hussein.
Afterward, Bowen said, the Pentagon and the fledgling Iraqi government shared responsibility for safeguarding some of the money; it was the Pentagon that asked him to investigate the whereabouts of the cash. A Pentagon spokesman contacted by CNN said the investigation found that "all of these funds remained under the control of the government of Iraq at all times."
The money came from the sale of Iraqi oil, and was diverted by international sanctions and stored at a Federal Reserve facility in the United States before being shipped to Iraq.
Though it was never U.S. taxpayer money, Americans may still be on the hook for some of it.
Iraqi officials have told Bowen they may sue to reclaim the lost money, and they may have a case, said Rep. Henry Waxman, D-California, the former chairman of the Oversight and Government Reform Committee.
"The truth of the matter is, the U.N. said to the United States, 'You are now entrusted with this money; you have a fiduciary responsibility for the Iraqi people to use it for their benefit,'" Waxman said. "And now we can't account for $6.7 billion."
The Iraqi Embassy in Washington did not respond to suggestions that Iraqi officials may have stolen some of the money, but a high-ranking Iraqi official said the inspector general's report has shown that "the United States failed to put in place accountable and transparent financial controls to safeguard Iraqi funds."
Already, fraud and abuse have been uncovered and a number of convictions obtained, Bowen said. He predicted that, before the matter is closed, there will be more prosecutions.