Where was German Concentration Camps Factual Survey filmed?

1945 documentary film directed by Sidney Bernstein, Baron Bernstein and Alfred Hitchcock

German Concentration Camps Factual Survey (2014) was filmed in Auschwitz, Dachau concentration camp, Buchenwald concentration camp, Bergen-Belsen concentration camp and Lublin-Majdanek concentration camp, 5 places named in its Wikipedia article's Production history section, in Poland, Germany. Wikidata records no filming location for it at all, so the article is the only recorded source. Each place says where its claim comes from.

See them on the map → Wikipedia Source data

Places per Wikipedia's Production history section

Wikipedia’s Production history section names 5 places. Each links to the sentence that says so.