Millions of dollars were wasted by the US-led Coalition Provisional Authority (CPA) that ran Iraq after the fall of Baghdad, a former official has said.
Franklin Willis said inexperience and poor security led to chaos
Huge cash payments were made to Iraqi contractors out of the back of pick-up trucks, in scenes reminiscent of the "Wild West," he said.
Former CPA officials told the US Senate that sackfuls of money were often "tossed about like footballs".
The former head of the CPA and the administration have denied wrongdoing.
The CPA ran Iraq for a year between June 2003 and June 2004.
The allegations were made on Monday at a Senate hearing into the authority's practices called by Senate Democrats.
The senators described the management of the CPA's multi-billion dollar reconstruction programme as a "scandal".
"We are close to 24 months into this conflict with Iraq and the administration still can't seem to get it right," said Senator Harry Reid.
Much of the US reconstruction budget for Iraq remains unspent
Senator Byron Dorgan, who heads the Senate Democratic Policy Committee that held Monday's hearing, said "millions, perhaps billions of dollars have been wasted and pilfered".
Former CPA official Franklin Willis told the hearing there had been widespread abuse and waste of money at the authority.
He showed pictures of himself and other US officials holding plastic-wrapped bundles of $100 notes totalling $2m, which he said was used to pay a security contractor.
"We told them to come in and bring a bag," Mr Willis said.
He added that "a combination of inexperienced officials, fear of decision-making, lack of communications, minimal security, no banks and lots of money to spend" led to chaos that was typical of the Wild West.
The hearing also heard reports of overcharging and fraud.
The allegations follow a report by the inspector general which said the CPA had transferred nearly $9bn to the interim Iraqi government without any controls.
Two years after the fall of Baghdad, 80% of the $18bn earmarked by the US Congress for Iraq's reconstruction remains unspent.
In a reply to the inspector general's report, former CPA head Paul Bremer said it was wrong to assume that "western-style budgeting and accounting procedures could be immediately and fully implemented in the midst of a war".
Bremer said there was no functioning Iraqi government and services were primitive or nonexistent when the authority took over in 2003.
A Pentagon spokesman also denied that the CPA has provided inadequate financial controls.