Anne Frank, whose diary became one of the most iconic portrayals of the Holocaust, died in a concentration camp in 1945 after she, her family and friends were discovered by security services while hiding in secret rooms in an office building in Amsterdam.

Anne's father, Otto Frank, was the only survivor of the eight Jews who spent more than two years hiding in the "Secret Annex" at 263 Prinsengracht. He suspected that his family and friends had been betrayed, perhaps by an untrustworthy employee of one of the offices below. Meanwhile, biographers theorized that perhaps relatives of the Franks' helpers ratted them out, leading to the family's arrest in August 1944. [Images: Missing Nazi Diary Resurfaces]

Now, new research suggests that the German Security Service may not have been looking for hidden Jews when they found Anne and the seven others hiding with her. Rather, they might have been investigating other activities at the office and simply stumbled across the hidden families by chance, according to historians at the Anne Frank House, the museum in Amsterdam dedicated to preserving the "Secret Annex" where Frank, her sister, her parents and four other Jews spent more than two years in hiding.

"The question has always been, who betrayed Anne Frank and the others in hiding?" historian Gertjan Broek wrote in a new paper released by the museum. "This explicit focus on betrayal, however, limits the perspective on the arrest."

In hiding

New documents about the employment of at least three of the policemen who raided the Secret Annex in 1944 reveal that these policemen weren't tasked primarily with hunting down Jewish people in hiding, Broek wrote. The Franks were living in secret rooms above Otto Frank's former company with another family, the van Pels, and a dentist named Fritz Pfeffer. The Franks had been in hiding, not setting a foot outdoors, since July 6, 1942. (The van Pels joined a week later, and Pfeffer arrived in November 1942.)

The circumstances of the discovery of Frank and the others have always been murky. Investigators arrived at the office building at 263 Prinsengracht in midmorning on Aug. 4, 1944, Broek wrote, and spent some time searching the premises. During the search, the Secret Annex, hidden behind custom-built bookshelves, was discovered. The Franks, the van Pels and Pfeffer were arrested. All were sent to concentration camps. Anne and her sister Margot died of typhus in February or March 1945 at Bergen-Belsen concentration camp.

Various theories have held that an employee of one of the companies in the office building, or perhaps a family member of someone who worked there, tipped off the German Security Service, called the Sicherheitsdienst, to the people in hiding. But no proof of a betrayer's identity has ever been found, Broek wrote.

A chance discovery?

Now, new documents suggest that perhaps there was no betrayer after all. Three of the confirmed members of the raiding party on the Secret Annex were longtime police officers whose work was related to cases involving cash, jewelry or confiscation of the belongings of Jews who were deported. One, Gezinus Gringhuis, was working not for the Sicherheitsdienst at the time of the raid, but for the Special Unit of the Central Investigation Division, Broek found. Thus, Broek wrote, Gringhuis' job wouldn't have involved searching for Jews in hiding. [Photos: Escape Tunnel at Holocaust Death Site]

On the other hand, Anne's diary mentions the arrest of two salesmen in the office building, Martin Brouwer and Pieter Daatzelaar, for ration-card fraud, or the illegal use or selling of the ration cards required to buy food. She writes that because of the arrest, the families in the Annex had no coupons for food, indicating that the family was fed, in part, by illegal ration cards. (Anne mentioned having to be quiet in the Annex so that Daatzelaar would not hear them, suggesting that the two ration-card dealers did not know they were there, Broek wrote.)

Because Gringhuis' job involved investigating economic violations such as ration-card fraud, the investigation that found the Franks might have been focused on other activities illegalized during the Nazi regime, Broek wrote. Such activities included a crime for which one of the Franks' helpers on the outside was arrested: "work refusal," or allowing people to work who had been called up for imprisonment in German forced-labor camps. ("Work refusal" referred to the refusal of the orders to participate in slave labor.)

"A company where people were working illegally and two sales representatives were arrested for dealing in ration coupons obviously ran the risk of attracting the attention of the authorities," Broek wrote. "While searching for people in hiding, fraud with ration coupons could be detected, since they [people in hiding] were often dependent on clandestine help. Conversely, investigating this kind of fraud might very well lead to the discovery of people in hiding."

The links between ration fraud and the investigators hasn't been proved, Broek warned, and it's still entirely possible that Anne, her family and their friends were betrayed. But focusing on betrayal has limited previous research on what happened to the Franks, he wrote.

"Clearly, the last word about that fateful summer day in 1944 has not yet been said," Broek wrote.

Original article on Live Science.