BAGHDAD, Iraq – The U.S. military launched a massive manhunt Saturday for three missing soldiers feared captured by insurgents after an ambush against their patrol in which five others were killed.

Details of the predawn attack are still sketchy, officials said, and the military is still trying to establish exactly what happened to the seven Americans and one Iraqi translator traveling in two Humvees in a notorious al-Qaida stronghold known as the Triangle of Death, 12 miles west of Mahmoudiya and around 20 miles southwest of Baghdad.

The hunt began at 4:44 a.m. local time Saturday when soldiers at a nearby command post heard an explosion and attempted to establish radio communications with the patrol. When they received no response, an unmanned aerial vehicle was launched.

Fifteen minutes later the UAV observed two burning vehicles. A quick-reaction force was dispatched, arriving at the scene an hour after the attack, at 5:44 a.m.

The force found five bodies, two burning Humvees and evidence of a firefight, but no sign of the three missing members of the patrol.

Troops immediately fanned out to see whether the soldiers were hiding nearby but found no trace of them, said spokesman Lt. Col. Christopher Garver.

The military has not been able to confirm whether the Iraqi translator was among the dead or missing, he said, suggesting that at least some of the bodies had been burned beyond immediate recognition.

Helicopters, unmanned aerial vehicles and planes were brought in to aid the search, checkpoints were set up across the area, and the military was soliciting the help of local tribal leaders to find the missing three.

“Make no mistake, we will never stop looking for our soldiers until their status is definitively determined, and we continue to pray for their safe return,” said military spokesman Maj. Gen. William Caldwell.

There was no immediate claim of responsibility, but the area is known as a stronghold for al-Qaida-affiliated Sunni insurgents.

The soldiers were serving under a new command established last month to focus on the troubled arc of territory to the south of Baghdad as part of the surge of troops being deployed to Iraq under President Bush’s new strategy. In keeping with military practice, the men’s names and unit were not identified pending notification of their families.

If the soldiers have been captured, it would be a rare coup for the insurgency, which routinely kills U.S. troops in bombings and shootings but has rarely seized captives.

In the most recent case, four U.S. soldiers were snatched in January from a government compound in the southern city of Karbala by men wearing American uniforms. The four were found dead nearby the next day.

Two soldiers abducted last June in Yusifiyah, a town just north of Mahmoudiya, were found tortured and bound together days later in the same region.

Two other soldiers are still missing; Sgt. Keith M. Maupin of Batavia, Ohio, who was abducted during an ambush on a fuel convoy in April 2004, and Ahmed Qusay al-Taie, an Iraqi-born reservist from Ann Arbor, Mich., who was abducted from a Shiite Baghdad neighborhood last October.