By Nick Childs
BBC Pentagon correspondent
Senior US army generals say the United States may have secretly held dozens of detainees in Iraq.
Holding prisoners in secret violates the Geneva Convention
They also accuse the CIA of not providing information on the subject.
The generals, who were testifying before a Senate committee, oversaw a key report into abuse of detainees at the Abu Ghraib prison near Baghdad.
An author of another report told another Congressional committee that the Bush administration bore some responsibility for the scandal.
'Up to 100'
At the Senate Armed Services committee, the generals said the number of "ghost" detainees may have been far higher than previously acknowledged.
These were prisoners held secretly and not notified to the International Committee of the Red Cross, in violation of the Geneva Conventions.
One general said there could have been up to 100 such prisoners, another said the number was more likely to be a couple of dozen.
But they said they did not know exactly because the CIA, which is being blamed for the practice, had not provided adequate information.
Independent commission urged
Meanwhile, one of the authors of another report into the scandal, former US Defence Secretary Harold Brown, appeared before the House of Representatives' Armed Services Committee.
He said the Bush administration as a whole shared some responsibility for the affair, for failing to prepare properly for post-war Iraq.
Eight senior retired officers, including some associated with Senator John Kerry's presidential campaign, have called for an independent commission of inquiry.