Baghdad, Iraq ? A small group of U.S. Marines alleged to have killed up to two dozen Iraqi civilians conducted a house-to-house hunt that stretched over three hours, while other Marines in Haditha did not intervene, according to an Iraqi human rights investigator.

Thaer al-Hadithi, a member and spokesman for the Hammurabi human rights association, a Sunni Muslim group, recounted with the help of a satellite map when and where Iraqi civilians cowered and sometimes died.

The case, which came to public attention two months ago because of a video released by the Hammurabi group, is threatening to further weaken popular support for the Iraq war in the United States and has tarnished the military’s image in Iraq and around the world.

The military, after initially saying the Iraqi deaths were the result of the roadside bomb and a subsequent gunfight with insurgents, has not publicly released updated findings.

But newer accounts, including details from briefings to members of Congress, have indicated at least some of the 24 deaths were the result of deliberate gunfire by a small group of Marines seeking revenge for the bombing, and that their actions were covered up by other Marines in the area who knew or suspected what had occurred.

Iraq also has ordered its own probe of the killings, with Prime Minister Nouri al-Maliki using unusually strong language to condemn them.

Al-Hadithi’s account is mostly in line with other, eyewitness reports. He said he expanded his personal observations at the time with follow-up interviews of other witnesses who saw actions that he could not see from his house. He made repeated visits to the restive town to get information, he said.

A native of the town, al-Hadithi was an administrator in the Haditha’s main hospital before he took leave to work with Hammurabi, which was set up 16 months ago.

Al-Hadithi, 42, said he had been visiting his family in Haditha in western Iraq for a Muslim holiday when he was awakened on the morning of Nov. 19 by an explosion that he later learned to be a roadside bomb that hit a U.S. convoy of four Humvees, killing one Marine.

According to U.S. lawmakers briefed by Pentagon officials, the Marines, enraged by the death of a comrade, stormed nearby homes, killing occupants as well as the driver and four passengers of a taxi.

Hush money paid?

On another front, one investigation of the alleged massacre in Haditha has focused on whether cash payments to the families of victims were part of a cover-up, sources said Wednesday.

The approval by officers of $2,500 payments to the families of 15 victims in the Haditha incident have been the main focus of a cover-up investigation by Army Maj. Gen. Eldon Bargewell, military and congressional sources said.

The Marines initially reported that the 15, including five girls ages 3 to 14, were killed by an insurgent’s roadside bomb, but they were all later found to have died of gunshot wounds.

A Marine headquarters spokesman said payments were made but said they were “not an admission of legal liability or fault.”

“Authority to approve such payments is normally held at the regimental level, but may be delegated to battalion commanders,” the spokesman said.

In the Haditha case, “There’s a gap in the whole narrative, you just don’t give them a bag of money” without officers concluding that the Marines bore some responsibility, said Catholic University Law Prof. Michael Noone, a former Air Force lawyer.

Noone said the cash payments made about a month after the shootings suggested that the command knew of possible wrongdoing well before the Naval Criminal Investigative Service began looking into the case in February.