Query: How many concentration camps were constructed in Hanover?
Context: A total of 2,400 people were deported, and very few survived. During the war seven concentration camps were constructed in Hanover, in which many Jews were confined. Of the approximately 4,800 Jews who had lived in Hannover in 1938, fewer than 100 were still in the city when troops of the United States Army arrived on 10 April 1945 to occupy Hanover at the end of the war.[citation needed]