According to documents released on Friday, an officer found that detainees "were being systematically and intentionally mistreated" at a jail near Mosul in December 2003.
The 311th Military Intelligence Battalion of the Army's 101st Airborne Division ran the lockup.
"There is evidence that suggests the 311th MI personnel and/or translators engaged in physical torture of the detainees," a memo from the investigator said. The January 2004 report said the prisoners' rights under the Geneva Conventions were violated.
Top military officials first became aware of the Abu Ghraib abuses in January 2004, when pictures such as those showing soldiers piling naked prisoners in a pyramid were turned over to investigators.
The resulting scandal after the pictures became public tarnished the military's image in Arab countries and worldwide and sparked investigations of detainee abuses.
The records about the Mosul jail were part of more than 1200 pages of documents referring to allegations of prisoner abuse.
The US Army released the records to reporters and to the American Civil Liberties Union (ACLU) which had filed a Freedom of Information Act lawsuit.
Abuses and possible torture were
reported throughout Iraq
"They show the torture and abuse of detainees was routine and such treatment was considered an acceptable practice by US forces," ACLU lawyer Amrit Singh said.
According to the report, the abuse included:
- Forcing detainees to perform exercises such as deep knee bends for hours on end, to the point of exhaustion
- Blowing cigarette smoke into the sandbags the prisoners were forced to wear as hoods
- Throwing cold water on the prisoners in a room that was between 4 and 10 Celsius in temperature
- Blasting the detainees with heavy-metal music, yelling at them and banging on doors and ammunition cans
No one was punished for the abuses, however, because the investigating officer said there was not enough proof against any individual.
The report did not say what actions might have amounted to torture or which individuals might have committed them.
The records released on Friday also contained details of several other abuse investigations. In one case, soldiers admitted they had rounded up suspected looters near Baghdad in the summer of 2003, then stripped them naked and told them to walk home.
"There is evidence that suggests the 311th MI personnel and/or translators engaged in physical torture of the detainees"
The staff sergeant in charge of that unit said he knew what he did was wrong but that he wanted to humiliate the looters so much they would never return.
He added another unit at their base had shot and killed a looter without being punished and he was afraid they would shoot others.
He was given an "other than honourable" discharge and two other soldiers involved in the stripping incident were given letters of reprimand, said army spokesman Colonel Jeremy Martin.
"The command took aggressive action to hold individuals accountable," Martin said.
In another incident, soldiers from a Howitzer battery beat three detainees in September 2003.
Martin said all four received non-judicial punishment, which can include letters of reprimand, fines, reductions in rank or detention.