New investigation
The new investigation was spurred by the tracking down of Karl Silberbauer, the SS non-commissioned officer who had led the arrests. The 1963 investigation was much more thorough than the one in 1948. Again, it pointed towards Willem van Maaren.
Silberbauer
In the 1950s, the diary of Anne Frank becomes world famous. Theatrical and screen versions follow on the heels of this fame. The unknown identity of the betrayer is increasingly seen as an unsatisfactory loose end. Tracking down Karl Siberbauer, the SD-officer in charge of the arrest, is the impetus for a new investigation. In 1963, famous Nazi-hunter Simon Wiesenthal finds Silberbauer in Vienna (Austria) where he is then working as a policeman. Silberbauer still remembers many of the details of the arrest, but not who the betrayer was. The person who had taken the telephone call, his superior, Julius Dettman, committed suicide shortly after the war ended. Silberbauer’s police duties are suspended during the course of the investigation, but because he had "only followed orders” during the arrest and had "acted correctly”, his old function is restored. He dies in 1972.
New witnesses
A number of new witnesses are questioned, yet unfortunately some of the important witnesses have already died. Kleiman died in 1959. The warehouseman Hartog and his wife are now also dead. Much more comes to light about Van Maaren, including the fact that he had actually committed the warehouse thefts of which he was suspected, but there is still no evidence to support the suspicion of betrayal. In 1964, the investigation is closed without concrete results. Willem van Maaren dies in 1971.