A soldier arrested on Wednesday over a video of British troops appearing to abuse Iraqi youths has been interviewed and released.
A Royal Military Police inquiry began last month after footage apparently showing Iraqi civilians being beaten up was published by the News Of The World.
The soldier was the fourth to be arrested over the video, shot in the southern Iraqi town of Al-Amarah.
Those involved are believed to be from the 1st Battalion The Light Infantry.
The video, taken in 2004, showed a group of up to 10 soldiers appearing to punch, kick and head-butt a number of young Iraqis, following a riot near their base.
A spokesman for the MoD said on Wednesday night that an investigation was still in progress.
"The Royal Military Police need time to conduct a thorough investigation to identify all those involved and failings that might have occurred," he said.
"Significant progress is being made. I can confirm four serving soldiers have now been arrested."
He said that, while British soldiers are expected to uphold the highest standards of behaviour, "they also deserve the same rights as British citizens".
"This means they remain innocent until proven guilty and they do not lose that right because they serve in uniform."