A US female soldier has been found guilty of indecent exposure after she took part in a mud wrestling party at the largest military prison in Iraq.
Camp Bucca was touted as a good example after Abu Ghraib scandal
The event was stage by military police at Camp Bucca prison near the southern port of Um Qasr last October.
The soldier has been demoted, but remains a guard at the camp. Others appearing in photos taken at the party have been reprimanded, officials said.
No Iraqi detainees were in the vicinity of the party, the army insists.
Military experts quoted by the New York Daily News, which first published details of the incident, said it showed a serious breakdown of military discipline.
Camp Bucca spokesman Barry Johnston put the incident down to "exuberance".
He denied a suggestion in the US media that alcohol may have been flowing, in contravention of a strict ban at the base.
Four inmates were shot dead by US guards during a riot at Camp Bucca in January. The military is investigating the shootings.
The treatment of Iraqi detainees held by US, UK and local forces has been a major Iraqi grievance since the US-led invasion of the country in 2003.
A scandal involving the US-run Abu Ghraib prison near Baghdad still sours US-Iraqi relations, after photographs were published showing soldiers taunting naked Iraqi prisoners.
The mud wrestling party occurred on 30 October as one military police battalion took over responsibility at the prison from another unit.
Photos were subsequently discovered at the base and handed over to camp commanders.
The Daily News says it has been given about 30 of the pictures and printed several of them on Sunday.
At least three female guards stripped to their underwear and wrestled in a pool full of mud.
The soldier has not been named by the US military, but is identified in the US press. She is one of several female soldiers captured on film exposing themselves to male soldiers.
She has been demoted to the rank of private first class.
"Detainees were nowhere in the vicinity," Mr Johnson said. "They had no possible way of seeing what occurred."
However, sources familiar with Camp Bucca quoted by the Daily News said prison security lights may have been trained on the scene - indicating that detainees could have seen or heard the commotion.