Troops surrounded the town of Youssifiyah and told residents over loudspeakers to stay inside, residents said. They then methodically searched the houses, focusing on possible secret chambers under the floors where the soldiers might be hidden, residents said. The soldiers marked each searched house with a white piece of cloth.
Soldiers also searched cars entering and leaving the town, writing "searched" on the side of each vehicle they had inspected. Several people were arrested, witnesses said.
The Islamic State in Iraq offered no proof for its claim that it was behind the attack Saturday in Mahmoudiya that also killed four U.S. soldiers and an Iraqi translator. But the Sunni area known as the "triangle of death" is a longtime al-Qaida stronghold.
Maj. Gen. William Caldwell, spokesman for the U.S. military, said 4,000 U.S. troops backed by aircraft and intelligence units were scouring the farming area as the military made "every effort available to find our missing soldiers."
The early morning attack on two U.S. military vehicles outside of Mahmoudiya, about 20 miles south of Baghdad, left the bodies of the four U.S. soldiers and their translator badly burned.
Caldwell said the bodies of the interpreter and three of the slain soldiers had been identified, but the military was still working to identify the fifth.
Later Sunday, the Islamic State of Iraq posted a brief message on a militant Web site saying it was responsible for the attack and held an unspecified number of U.S. soldiers. The group promised more details later.
The Islamic State is a coalition of eight insurgent groups. Late last month, it named a 10-member "Cabinet" complete with a "war minister," an apparent attempt to present the Sunni coalition as an alternative to the U.S.-backed, Shiite-led administration of Prime Minister Nouri al-Maliki.
U.S. military officials said they had no indication of who was behind Saturday's attack.
"It's difficult to verify anything that al-Qaida in Iraq would say because they lie," said Lt. Col. Christopher Garver, a military spokesman. However, "it would not surprise us if it were al-Qaida behind this, because we've seen this type of attack, this type of tactic, before."
Talk Show America 5/14/2007