A Marine captain has been told he will be criminally charged in connection with the killing of 24 civilians in the Iraqi town of Haditha, his attorney said Monday.

Capt. Lucas McConnell, 31, was told by his commanding officer that he will be charged with dereliction of duty, said Kevin McDermott, his attorney.

"We're just absolutely clueless as to what kind of dereliction of duty he could have committed," he said, adding that his client was not present during the killings.

Separately, two military officials said a group of Marines would be charged Thursday for their alleged roles in the killings. The officials requested anonymity because they were not authorized to speak publicly about the charges ahead of their announcement.

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The charges would mark the latest step in a massive investigation into the actions of a squad of Camp Pendleton-based Marines and several officers on Nov. 19, 2005. Earlier this month, the Marine Corps said that charges were being finalized against several troops but the precise timing was unclear.

Marine spokesman Lt. Col. Sean Gibson said Monday: "We will be presenting as much information as allowable at the appropriate time."

The Marine Corps initially reported that 15 civilians died in a roadside-bomb blast. Citing survivor accounts and human rights groups, a media report in March said that the killings were deliberate acts by the Marines, prompting the criminal investigation.

A parallel military investigation has examined whether officers in the Marines' chain of command tried to cover up the events. Results have not been made public.

The killing began when a roadside bomb struck the last of a four-vehicle convoy containing a 12-Marine squad and several Iraqi soldiers. Driver Lance Cpl. Miguel Terrazas died in the blast and two other Marines were seriously wounded.

In the events that followed, two dozen Iraqis were killed. Five men were shot to death when they approached the scene in a taxi, and others — including women and children — died in three houses over the next several hours.

Neal Puckett, a defense attorney for squad leader Staff Sgt. Frank D. Wuterich, has described the events of the day as a tragic but lawful combat engagement.

The criminal case will focus on whether the Marines were responding to perceived threats with legitimate force, or if the troops went too far and acted outside their rules of combat.