On the morning of 4 August 1944, the "Achterhuis" was stormed by a group of German uniformed police ("Grüne Polizei") led by SS-"Oberscharführer" Karl Silberbauer of the "Sicherheitsdienst". The Franks, Van Pelses, and Pfeffer were taken to RSHA headquarters, where they were interrogated and held overnight. On 5 August they were transferred to the Huis van Bewaring (House of Detention), an overcrowded prison on the Weteringschans. Two days later they were transported to the Westerbork transit camp, through which by that time more than 100,000 Jews, mostly Dutch and German, had passed. Having been arrested in hiding, they were considered criminals and sent to the Punishment Barracks for hard labour.