Other suspects
In 1998, Melissa Müller, in her biography about Anne Frank, suggests a woman named Lena-Hartog van Bladeren as a possible suspect. Two years later, another writer, Carol Anne Lee, presents a new theory in her biography about Otto Frank. She believes the guilty party is Tonny Ahlers, an acquaintance of Otto Frank.
Lena Hartog-van Bladeren
In 1998, Melissa Müller’s book Anne Frank, The Biography was published. In this book, the author states that the other warehouseman Lammert Hartog, as well as his wife Lena Hartog-Van Bladeren, must have also known that there were Jews being hidden in Opekta's building. Not only did she work as a cleaning lady at 263 Prinsengracht, she also cleaned the home of Petrus and Anne Genot. Petrus Genot happened to work for the company owned by Kleiman’s brother.
When Lena Hartog was questioned in 1948, she neglected to mention to the police that she had worked on the Prinsengracht. According to the 1948 testimony of Anna Genot, Lena told her, in July 1944, that she was terribly concerned about the safety of her husband because Jews were being hidden on the Prinsengracht. Lena also supposedly said to Bep that they would all be in grave danger if this were discovered.
In her book, Melissa Müller suggests the possibility that the people in hiding were betrayed by Lena Hartog-Van Bladeren. There is however no proof to substantiate this. What is clear though, is that the 1948 investigation as well as the one conducted in 1963-64 were both too preoccupied with Willem van Maaren. The role played by Lena Hartog-Van Bladeren and her husband was never seriously investigated.
Tonny Ahlers
Otto Frank and Tonny Ahlers meet for the first time in April 1941, long before the Frank family goes into hiding. Apparently, Otto Frank expresses his doubts about a German war victory to an acquaintance he runs into and this person then sends a letter to the Gestapo informing on him. Tonny Ahlers, who is active in the NSB (Dutch Nazi-party) and knows many people who work for the Security Police, somehow gets hold of this letter. In return for his silence, Ahlers blackmails Otto for money. According to the writer Carol Anne Lee, this was not a solitary incident and Tonny Ahlers continues to blackmail Otto. After the war, Ahlers claimed that he knew about the people being hidden in the Secret Annex. Therefore, as far as Carol Anne Lee is concerned, Tonny Ahlers was the person who betrayed the people in hiding.