KABUL - A U.S. military official says probable cause has been found to keep holding an American soldier suspected in a shooting spree that killed 16 Afghan civilians.

The soldier, who has not been named, is accused of leaving a U.S. base in Panjwai district of southern Kandahar province and gunning down the Afghan civilians, including nine children and three women, in the middle of the night between Saturday and Sunday.

Col. Gary Kolb, a spokesman for the U.S.-led military coalition in Kabul, says a 48-hour probable cause assessment has been completed and that the service member continues to be confined.

U.S. Secretary of Defence Leon Panetta has said that the soldier could face capital punishment.