The Jewish diarist went into hiding in some concealed rooms behind a bookcase in the building where Anne’s father, Otto Frank, worked in 1942. The family was arrested by the Gestapo in 1944 and transported to concentration camps.
Anne died in a Nazi concentration camp in 1945 at the age of 15 after two years in hiding in Amsterdam.
Her diary, which was published after her death, is the most famous first-hand account of Jewish life during the war.
While there have been persistent claims of betrayal by an informant, the source of the information that led authorities to the Franks has never been identified.
Now, a team including a former FBI agent believes Arnold van den Bergh, a Jewish figure in the Dutch capital, probably “gave up” the Franks to save his family.
According to reports, van den Bergh had been a member of Amsterdam’s Jewish Council, the body forced to implement Nazi policy in Jewish areas.
The body was disbanded in 1943 and its members were sent to concentration camps.
But the investigative team found van den Bergh was not sent to a camp but instead lived in Amsterdam as normal at the time.
They suggested a member of the Jewish Council had been feeding the Nazis information.
Former FBI agent Vince Pankoke told CBS 60 Minutes: “When van den Bergh lost all his series of protections exempting him from having to go to the camps, he had to provide something valuable to the Nazis that he’s had contact with to let him and his wife at that time stay safe.”
The investigative team – which also includes historians and experts – spent six years using modern techniques to crack the case.
These included using computer algorithms to search for connections between many different people, the BBC reported.
The team said they struggled with the revelation another Jewish person could have been the betrayer.
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But they also found evidence Anne’s father may himself have known and kept it secret.
In the files of a previous investigator, the team found a copy of an anonymous note sent to Mr Frank identifying van den Bergh as his betrayer.
Mr Pankoke added anti-Semitism may have been the reason it was never made public.
He added: “Perhaps he just felt that if I bring this up again… It’ll only stoke fires further.
“But we have to keep in mind that the fact that [van den Bergh] was Jewish just meant that he was placed into an untenable position by the Nazis to do something to save his life.”
According to Dutch newspaper de Volkskrant, van den Bergh died in 1950.
In 1960, the Anne Frank House opened but while they were not part of the investigation, they said it was “impressed” with it.
Executive director, Ronald Leopold, added the new research had “generated important new information and a fascinating hypothesis that merits further research”.
The House shared its archives and museum with the team to help in their research.