US military authorities are investigating Marines in connection to the killing of Iraqi prisoners during the battle for Fallujah in 2004, a government spokesman confirmed Friday, according to dpa. Ed Buice, a spokesman for the Naval Criminal Investigative Service, would not discuss details of the case and said no charges have so far been filed. Investigators were looking into "credible allegations of wrongdoing made against US Marines concerning actions said to have taken place in Fallujah, Iraq in the fall of 2004," Buice said. US media reported that at least 10 Marines were the focus of the probe into the killing of eight Iraqi prisoners captured during heavy fighting in November 2004 in the central Iraqi city. The US military has filed charges against other Marines and US Army soldiers for the killing of Iraqi civilians. The most notorious case is the November 2005 wrongful killings of 24 civilians in Haditha. Three Marines have been charged with murder in that case. US forces launched the major assault on Fallujah, which lies in Anbar province, in November 2004 to wrestle control of the city from insurgents and al-Qaeda militants. The fighting was some of the fiercest since Saddam Hussein's regime was toppled. The door-to-door combat left much of the city destroyed.