Five U.S. Army soldiers are being investigated for allegedly raping a young woman, then killing her and three members of her family in Iraq, a U.S. military official told The Associated Press on Friday.

Iraqi soldiers man a checkpoint on a bridge in central Baghdad, Iraq Friday, June 30, 2006 just before the Friday vehicle ban came into effect. The 11am to 3pm vehicle ban on Fridays was introduced by Iraqi Prime Minister Nouri al-Maliki in an attempt to prevent car bombings on Iraqis gathering to give traditional Friday muslim prayers. [AP]

The soldiers also allegedly burned the body of the woman they are accused of assaulting in the March incident, the official said on condition of anonymity because of the sensitivity of the case.

Maj. Gen. James D. Thurman, commander of coalition troops in Baghdad, had ordered a criminal investigation into the alleged killing of a family of four in Mahmoudiyah, south of Baghdad, the U.S. command said. It did not elaborate.

The case represents the latest allegations against U.S. soldiers stemming from the deaths of Iraqis. At least 14 U.S. troops have been convicted.

The United States also is investigating allegations that two dozen unarmed Iraqi civilians were killed by U.S. Marines in the western town of Haditha on Nov. 19 in a revenge attack after one of their own died in a roadside bombing.

"The entire investigation will encompass everything that could have happened that evening. We're not releasing any specifics of an ongoing investigation," said military spokesman Maj. Todd Breasseale.

"There is no indication what led soldiers to this home. The investigation just cracked open. We're just beginning to dig into the details."

However, a U.S. official close to the investigation said at least one of the soldiers, all assigned to the 502nd Infantry Regiment, has admitted his role and has been arrested. Two soldiers from the same regiment were slain this month when they were kidnapped at a checkpoint near Youssifiyah.

The official said the accused soldiers were from the same platoon as the two slain soldiers, whose bodies were mutilated. He said the mutilation of the slain soldiers stirred feelings of guilt and led at least one of them to reveal the rape-slaying on June 22.

At least four other soldiers have had their weapons taken away and are confined to Forward Operating Base Mahmoudiyah south of Baghdad.

The official said the killings appear to be unrelated to the kidnappings. He said those involved were all below the rank of sergeant. Senior officers were aware of the family's death but believed it was due to sectarian violence, common in the religiously mixed town, he said.

The killings appeared to have been a "crime of opportunity," the official said. The soldiers had not been attacked by insurgents but had noticed the woman on previous patrols.