A top US commander has ordered an inquiry into the deaths of three Iraqi prisoners in military custody.
The probe comes after soldiers raised suspicions about the deaths
The three died in early May while being held by coalition forces in Salahuddin province, north of Baghdad.
The probe was triggered by soldiers who raised suspicions about the deaths, said Lt Gen Peter W Chiarelli, head of multinational forces in Iraq.
It is the latest in a series of inquiries into the alleged abuse or killing of Iraqis by coalition forces.
A statement by Gen Chiarelli released by the US army said the investigation would examine the "circumstances surrounding the deaths of three males in coalition force custody in southern Salahuddin province on or about 9 May 2006".
"The request for an investigation is the result of soldiers' reported suspicions about the deaths," he said, without giving further details.
The criminal investigation comes just weeks after a US military probe cleared US troops of any wrongdoing in the deaths of an Iraqi family in the town of Ishaqi in March.
On Friday, the US military said a probe into an alleged massacre at Haditha in November had been completed and was being reviewed by Gen Chiarelli.
Another investigation is being held into claims that an Iraqi man was deliberately killed in April in Hamdaniya - and that the circumstances were covered up.
The US marine corps is also investigating a video which allegedly shows a marine singing a song about Iraqi civilians being killed by insurgents.