The U.S. military in Iraq is investigating whether American soldiers disobeyed orders to conduct a re-supply mission north of Baghdad because they thought they lacked adequate protection.

At issue is whether 19 members of a unit that delivers food and water to other soldiers in combat zones refused an order to report for duty Wednesday. Relatives of some of the reservists say the troops told them how they felt they did not have adequate protection to conduct an assigned resupply mission in a combat zone.

A statement issued by the U.S. military command in Baghdad says the soldiers raised some valid concerns, but also describes the incident as a temporary breakdown in discipline, a serious military offense.

Military resupply convoys were often targeted during the war that toppled Saddam Hussein and have repeatedly come under attack by insurgents in Iraq in the time since. The U.S. military is describing this as an isolated incident and denies allegations that any of the soldiers who allegedly refused the deployment order are being detained or arrested.