Senior US Army generals in Iraq were told in December 2003 that special operations troops and CIA personnel were suspected of abusing Iraqi prisoners.
A December 2003 report on suspected prisoner abuse indicates the US leadership in Iraq knew about prisoner treatment before photographs of detainees being abused at Abu Ghraib jail emerged within the military in the middle of January.
The report by retired Col. Stuart Herrington, requested by the senior US military intelligence officer in Iraq, found that some prisoners turned over to the US military by members of an elite task force had injuries suggesting they may have been beaten while in custody, said the defence officials.
The suspected abuse detailed in the Herrington report did not take place in Abu Ghraib.
The report also provided an early warning about the practice by some US forces of keeping "ghost detainees" - prisoners kept off the books and hidden from the International Committee of the Red Cross.
US officials disputed the notion that the warning had been ignored.
When the abuse photographs, including ones showing a US female soldier holding a naked prisoner on a leash, were shown on US television, they prompted calls by political opponents and human rights activists for US Defence Secretary Donald Rumsfeld to resign.
The Pentagon said it was investigating but the existence of the 2003 report was not revealed.
Col Herrington found that a mixture of Army and Navy special operations troops and CIA personnel searching for high-ranking Iraqi fugitives and weapons of mass destruction had taken prisoners to an undisclosed interrogation facility in order to keep their actions secret, officials said.
The report also found some of the detention activities at the time may have been "technically" unlawful, officials said.