All non-Dutch Jews were also sent to Westerbork. In addition, over 15,000 Jews were sent to labour camps. Deportations of Jews from the Netherlands to German-occupied Poland and Germany began on 15 June 1942 and ended on 13 September 1944. Ultimately some 101,000 Jews were deported in 98 transports from Westerbork to Auschwitz (57,800; 65 transports), Sobibor (34,313; 19 transports), Bergen-Belsen (3,724; 8 transports) and Theresienstadt (4,466; 6 transports), where most of them were murdered. Another 6,000 Jews were deported from other locations (like Vught) in the Netherlands to concentration camps in Germany, Poland and Austria (like Mauthausen). Only 5,200 survived. The Dutch underground hid an estimated number of Jews of some 25,000–30,000; eventually, an estimated 16,500 Jews managed to survive the war by hiding. Some 7,000 to 8,000 survived by fleeing to countries like Spain, the United Kingdom, and Switzerland, or by being married to non-Jews (which saved them from deportation and possible death). At the same time, there was substantial collaboration with the Nazis from members of the Dutch population, including the Amsterdam city administration, the Dutch municipal police, and Dutch railway workers, who all helped to round up and deport Jews.