A spokesman, Major General William Caldwell, said the arrests were made in Anbar province, west of Baghdad. He said the Marines have identified several locations where kidnappers held Carroll
Caldwell said U.S. and Iraqi authorities are discussing options for trying the men.
Elsewhere in Iraq, the U.S. military said it is searching for two American crew members missing after their Army helicopter crashed west of Baghdad.
Four others on board were injured and are in stable condition. U.S. officials say they do not believe enemy fire caused the helicopter to crash.
Meanwhile, in Baghdad, a roadside bomb apparently targeting a U.S. patrol killed a bystander. In Basra, southern Iraq, gunmen killed a senior army official.
Earlier, in Baquba, an explosion killed at least four people and damaged a mosque in the city. There were conflicting reports about what caused that blast.
