By the end of WWII, over 31,000 suspected enemy aliens and their family members had been interned for at least a time at enemy alien internment camps run by the Immigration and Naturalization Service. Many were paroled or released following an appearance before a local hearing board. Several thousand were repatriated to their native country, some voluntarily and others involuntarly. At the end of the war, internees no longer deemed "dangerous" were released, although it took until 1948 before the last internment camp was closed.
Records relating to the internment of World War II enemy aliens are located in several different record groups in the custody of the National Archives. The index to the WWII Alien Enemy Detention and Internment Case Files can be searched online in ARC (Archival Research Catalog).
The United States was not the only country to intern alien civilians during WWI and WWII. The Isle of Man was used as a base for Alien Civilian Internment Camps during both wars. The National Archives of Australia holds records of internment camps and the enemy aliens held there during both World War I and World War II. Canada held over 8500 "enemy aliens" in internment camps, of which over 5,000 were Ukranians, in the period following the outbreak of WWI, and obliged an additional 80,000 individuals to register as "enemy aliens." Similar internment camps existed in France, Germany and other countries around the world.