The first investigation
Following the war, Kleiman and the other Helpers are increasingly occupied with the question of who the betrayer was. Immediately after the end of the war, Kleiman writes a letter to the Politieke Opsporings Dienst [POD] (the Dutch equivalent of the FBI). The POD had as its task hunting down people who collaborated with the German occupier.
Van Maaren under suspicion
In the letter, Kleiman expresses his suspicions about Van Maaren and asks the POD to conduct an investigation. Yet, nothing is done with the letter for two years. Finally in 1948 an investigation is set in motion, probably resulting from a discussion Otto Frank has with the Politieke Recherche Afdeling (PRA or literally Political Investigation Department) of the Amsterdam Police Department.
Shoddy
The police question the helpers Miep, Kleiman and Kugler; the warehouse employees Van Maaren and Hartog; as well as others who worked in the warehouse. Hartog testifies that Van Maaren had told him two weeks before the raid that there were Jews being hidden upstairs. Certainly, Hartog’s wife could also have known. In looking back, little can be said about the quality of the investigation. Many questions were not asked and few people were interrogated. It was a shoddy investigation, and it is brought to a close because no evidence is turned up. Fourteen years will pass before a new investigation takes place.