Mr. Bowen said that because he suspected that completed projects were not being maintained, he had ordered his inspectors to undertake a wider program of returning to examine projects that had been completed for at least six months, a phase known as sustainment.

Exactly who is to blame for the poor record on sustainment for the first sample of eight projects was not laid out in the report, but the American reconstruction program has been repeatedly criticized for not including in its rebuilding budget enough of the costs for spare parts, training, stronger construction and other elements that would enable projects continue to function once they have been built.

The new reports provide some support for that position: a sophisticated system for distributing oxygen throughout the Erbil hospital had been ignored by medical staff members, who told inspectors that they distrusted the new equipment and had gone back to using tried-and-true oxygen tanks — which were stored unsafely throughout the building.

The Iraqis themselves appear to share responsibility for the latest problems, which cropped up after the United States turned the projects over to the Iraqi government. Still, the new findings show that the enormous American investment in the reconstruction program is at risk, Mr. Bowen said.

Besides the airport, hospital and special forces barracks, places where inspectors found serious problems included two projects at a military base near Nasiriya and one at a military recruiting center in Hilla — both cities in the south — and a police station in Mosul, a northern city. A second police station in Mosul was found to be in good condition.

The dates when the projects were completed and deemed successful ranged from six months to almost a year and a half before the latest inspections. But those inspections found numerous instances of power generators that no longer operated; sewage systems that had clogged and overflowed, damaging sections of buildings; electrical systems that had been jury-rigged or stripped of components; floors that had buckled; concrete that had crumbled; and expensive equipment that was simply not in use.

Curiously, most of the problems seemed unrelated to sabotage stemming from Iraq’s parlous security situation, but instead were the product of poor initial construction, petty looting, a lack of any maintenance and simple neglect.