BAGHDAD , Iraq ( CNN ) -- Five American security contractors were detained in connection with the killing of another American contractor last month inside Baghdad 's Green Zone , sources with knowledge of the investigation told CNN Saturday . The body of James Kitterman was found in a car in Baghdad 's heavily protected Green Zone . Iraqi and U.S. personnel took the five into custody in an operation inside the Green Zone before dawn on Friday , according to an Iraqi official involved in the investigation into the killing of James Kitterman . The five , who have not yet been charged , were being held by Iraqi security forces Saturday at a jail inside the heavily protected zone , he said . The troops also confiscated weapons during the raid on the suspects ' firm at about 4 a.m. ( 11 a.m . ET ) , said the official , who spoke on condition of anonymity . The names of the suspects and the company they work for were not released . The U.S. military declined comment and referred questions to the U.S. Embassy in Baghdad . Embassy officials did not immediately respond to request for comments . Kitterman was found bound , blindfolded and fatally stabbed in a car in the district , formally known as the International Zone , on May 22 . The 60-year-old Houston , Texas , resident owned a construction company that operated in Iraq . The five suspects knew the victim , a source inside the Green Zone familiar with the investigation said . Both the Iraqi and the Green Zone sources noted that the FBI has been involved in the investigation from the start . Once the suspects are charged and referred to trial , the case would be sent to Iraq 's Central Criminal Court , the Iraqi official said . If that happens , it would be the first time U.S. citizens were tried in Iraq since the United States returned the country 's government to the Iraqis . CNN 's Mohammed Tawfeeq and Alan Duke contributed to this report .
NEW : Weapons confiscated in raid of suspects ' firm , official says . five arrested in death of fellow contractor Kitterman . James Kitterman found bound , blindfolded and fatally stabbed . the U.S. Embassy owned a construction company that operated in the International Zone .