NORTH COUNTY - An official probe is under way into "credible allegations" that a group of Camp Pendleton Marines killed several Iraqi prisoners of war in 2004, federal investigators confirmed Monday.

A spokesman for the Naval Criminal Investigative Service in Washington confirmed the probe in a written statement sent to the North County Times in response to an inquiry from the newspaper last week. The newspaper first reported the matter in its Saturday editions.

"NCIS can confirm that it is conducting an investigation into credible allegations of wrongdoing made against U.S. Marines concerning actions said to have taken place in Fallujah Iraq in the fall of 2004," said the statement from agency spokesman Ed Buice.

Multiple sources have said the inquiry surrounds five to 10 Marines from Camp Pendleton who took part in a battle in Fallujah in November 2004.

A source with direct knowledge of the investigation told the North County Times last week that about 20 current and former Marines have been interviewed and that several have been read their rights, an indication that criminal charges could result.

Under the Uniform Code of Military Justice, the killing of a captured enemy combatant who does not present a threat is considered murder.

The Marines are believed to have been involved in the deaths of as many as eight insurgents who had been captured during the battle, according to the sources.

It remained unclear Monday whether the Iraqis had been officially declared prisoners and whether any or all were bound in any way. The incident reportedly took place on or about Nov. 10, 2004.

In the statement issued Monday, Buice wrote that the NCIS would not say anything further about the investigation at this point.

"The Naval Criminal Investigative Service is a fact-finding organization and information gathered will be presented to the appropriate authority who will decide whether further action is warranted," the statement read. "Beyond confirming the existence of the investigation, NCIS policy is to make no comment about the details of an open case."

One of the Marines has said that the troops believed they were carrying out the orders of their commanders when the insurgents were shot, according to one source.

The Department of the Navy law enforcement agency is composed of civilian investigators who are not under Marine Corps control.

Sources have said the Fallujah investigation arose as a result of the ongoing prosecution of three Camp Pendleton enlisted Marines charged with murder in the deaths of 24 Iraqi civilians in the city of Haditha on Nov. 19, 2005. Four officers face charges of dereliction of duty for failing to fully investigate those deaths.

None of the men being prosecuted in the Haditha case or an incident in Hamdania, Iraq, last year are subjects of the investigation into the alleged Fallujah killings, a source said. Some enlisted men whose testimony was sought during recent hearings in the Haditha incident were pulled from the witness list because they were involved in the Fallujah investigation.

In the Hamdania case, five of eight Camp Pendleton troops have pleaded guilty for their roles in the abduction and shooting of a retired Iraqi policeman in April 2006. Three defendants face trial this summer.

The battle for Fallujah was one of the largest concentrated battles following the March 2003 invasion of Iraq. It came after the insurgency took control of the city after U.S. forces left it in April of that year.

On Nov. 6, 2004, a main group of troops from Camp Pendleton's 3rd Battalion, 1st and 5th Marine Regiments, along with supporting Marine units and U.S. Army forces, massed and launched an assault to wrest control of Fallujah. Insurgent forces had taken over the city after U.S. forces had withdrawn in April 2004.

Intense fighting took place during the next week with the final resistance cleared by late December. Several Camp Pendleton Marines were later honored with awards such as the Navy Cross for valorous actions during the fighting.

- Contact staff writer Mark Walker at (760) 740-3529 or mlwalker@nctimes.com.