Congress will hold hearings on a deadly shooting incident involving Marines firing on unarmed Iraqi civilians in the Iraqi town of Haditha last November, the House Armed Services Committee chairman said Friday.

Rep. Duncan Hunter, R-Calif., said he will hold the hearings after the ongoing criminal investigation is completed; that could be as early as next week.

"If there were problems in the chain of command, if there was a cover up, if there was anything that wasn't reported, let the chips fall where they may but don't presume anything," Hunter said.

Senior military commanders told FOX News on Thursday that there was a criminal investigation probing the incident. No conclusions have been reached in the investigation, according to Pentagon spokesman Bryan Whitman.

Three Marines have already been relieved of their command in response to the shootings of at least 15 civilians in the Anbar province. A report is being crafted on the incident but is not likely to be finished for another week or two.

"This report is going to be ugly," one commander said, adding that it appears the Marines did not follow the rules of engagement.

The private comments from senior commanders and various Pentagon officials come after Rep. Jack Murtha, D-Pa., mentioned the report in a news conference Wednesday to mark the six-month anniversary since he called for the redeployment of U.S. troops out of Iraq.

Senior commanders said Murtha is "coming from a position of knowledge." Marine commanders declined to respond to Murtha's comments, citing the ongoing investigation.

Murtha, a strong opponent of the war, said the investigation is going to show that innocent civilians were killed "in cold blood."

"This is going to be a very bad thing for the United States," he said.

Murtha said at least 15 Iraqis, including women and children, were killed in a firefight following an insurgent attack on Marines that left one dead.

On Friday, Hunter responded to Murtha's comments by saying, "I don't want to see these troops who have done such a magnificent job end up being portrayed in the American media by what comes out of the Haditha investigation."

"That's one incident, one squad, one day last November," he added.

Military officials said in November that the Marines were responding to improvised explosive devices and small arms fire attacks on their convoy. A U.S. military statement described it as an ambush on a joint U.S.-Iraqi patrol that left 15 civilians, eight insurgents and a U.S. Marine dead in the bombing and a subsequent firefight.

But several news accounts, including one by Time magazine, quoted witnesses as saying Marines responded to the IED by firing indiscriminately on civilians in a residential area. Reportedly, photos were taken of the scene that do not support the Marines' original account of how the incident evolved. In all, 15 members of two families, including a 3-year-old girl, were killed, but not by the IED, locals say.

Click here to read the Time magazine article.

"There was no firefight, there was no explosion that killed the civilians in a bus. There was no bus. There was no shrapnel, there was only bullet holes inside the house where the Marines had gone in," said Murtha, a Marine veteran. "There was no IED that killed these innocent people. Our troops overreacted because of the pressure on them and they killed innocent civilians in cold blood. And that's what the report is going to tell."

Speaking to reporters on Thursday, House Minority Leader Nancy Pelosi applauded Murtha for bringing the issue to the fore.

"This is a tragedy. It's very sad, but I think it's important for the administration to release the report. They know it's ready. They've been holding it back. I believe that's why Mr. Murtha spoke out about it," she said.

Asked whether this incident was being glossed over, Defense Secretary Donald Rumsfeld told FOX News' Bill O'Reilly that if the investigation finds wrongdoing, the right people will be held accountable.

"Needless to say, we have to take seriously allegations of that type, and they're under investigation and they will then be handled in the normal order of things," Rumsfeld said.

Murtha used the incident to point out that the stress on U.S. troops is too intense, and he repeated his call for all U.S. troops to leave Iraq as soon as possible.

"I feel that the tremendous pressure and the redeployment over and over again is a big part of this. These guys are under tremendous strain, more strain than I can conceive of. And this strain has caused them to crack in situations like this," Murtha said.

"It's not caused only by the troops, it's caused by the fact there's so few of them, and they go out every day, and 42 percent of them don't understand what the mission is," he added.

Murtha emphasized that the U.S. military is constantly barraged by attacks, but staying there is just a diversion sought by countries that want to distract the United States from the larger War on Terror.

"I'll tell you who wants us in Iraq: Iran, Russia, China and North Korea and Al Qaeda. There's only 1,000 Al Qaeda, 1,000 Al Qaeda. The rest are Iraqis that we're caught in between," he said.

"I'm convinced that there'll be continued chaos, because it's a civil war. But like our civil war, only [the Iraqis] can handle it."

FOX News' Bret Baier and Nick Simeone contributed to this report.