Iraqi soldiers and civilians cross a damaged bridge Saturday over Diyala river in southern Baghdad. Twin suicide car bombers struck police checkpoints at bridges in a predominantly Shiite area of Baghdad, killing at least 23 people just hours after a series of U.S. raids on car bomb networks around the capital killed four suspected insurgents.

Baghdad ? U.S. and Iraqi troops searched house-to-house and combed fields with their bare hands Saturday after American troops and their Iraqi interpreter came under attack in the notorious “triangle of death” south of Baghdad, leaving five dead and three missing.

The military said the patrol was struck in a predawn explosion near Mahmoudiya, about 20 miles south of Baghdad – an al-Qaida area where two U.S. soldiers were found massacred after disappearing at a checkpoint nearly a year ago.

A nearby unit heard the blast and the search was launched after communication could not be established with the patrol, the military said. Shortly after the blast, a drone observed two burning vehicles.

An emergency response unit arrived at the scene and found five members of the team dead and three others missing.

Checkpoints were established throughout the area, while helicopters and jets buzzed overhead. AP Television News footage showed Iraqi soldiers picking through cattails and other weeds as they searched fields and canals for clues.

Lt. Col. Christopher Garver, a U.S. military spokesman, said the search would continue throughout the night.

“A lot of our vehicles have thermal capabilities, which sometimes work better at night than they do during the day,” he said.

The military refused to specify whether the Iraqi interpreter was among those killed or missing and would not give more details about where the bodies were found.

An Iraqi army officer who was familiar with the search said he saw five badly burned bodies inside a Humvee at the site, suggesting the remains may not have been recognizable.

The officer spoke on condition of anonymity because he was not authorized to disclose the information.

He also said joint U.S.-Iraqi forces had sealed off the area and were conducting house-to-house searches, rounding up dozens of suspects. The military declined to comment on detentions but said troops were looking for suspects.

The Iraqi officer said U.S. troops singled out seven suspects out of as many as 50, including a wounded man who was hiding in a house and confessed to participating in the attack.

He said most of the houses searched near the attack contained only women and children because the men had fled, fearing arrest.

“I was in my cucumber field when I heard a big explosion followed by shootings. I ran toward my house because I was afraid that I would be arrested if spotted in the field,” Mizaal Abdullah, a 37-year-old farmer who was in the custody of the Iraqi army, said by telephone. “This is the third time that I have been arrested. Each time, the real attackers flee the area and innocent people like me get arrested.”

The attack occurred at 4:44 a.m. about 12 miles west of Mahmoudiya, a town of about 65,000 in a Sunni area dubbed the “triangle of death” for the frequent attacks against Shiite civilians and U.S. and Iraqi forces.