Who betrayed Anne Frank? Investigators claim they've cracked 75-year-old mystery

Anne Frank and her family may have been given up to the Nazis by a Jewish businessman, a new investigation has found.

Ms Frank, a Jewish teenager in Nazi-occupied Amsterdam, fled into hiding with her family in 1942. She kept a diary during her two years in a secret annex, until the family was arrested and deported to concentration camps, where Ms Frank died.

75 years after its publication, 'The Diary of Anne Frank' remains a world-famous account of Jewish life during the war, yet no one has been able to prove who alerted the Nazis to her hiding place.

Now, a team of investigators have told CBS that Arnold van den Bergh, a Jewish man, betrayed the Franks in order to protect his own family from the Nazis.

Ex-FBI agent Vince Pankoke led the team, which also comprised of historians and other experts. They built on previous investigations with modern investigative techniques, like using artificial intelligence to sift through documents.

After six years of digging, the team presented its findings to CBS' '60 Minutes' show.

Mr Pakoke said the team looked at dozens of suspects before arriving at Mr Van den Bergh, who served on the Amsterdam Jewish Council. The group implemented Nazi policies within their community, in return for a chance of being spared the camps.

"I'd call [Mr Van den Bergh] a chess player. He thought in terms of layers of protection, by obtaining different exemptions from being placed into the camps," Mr Pankoke said.

The team found that Mr Van den Bergh lived an open life in Amsterdam at a time when Jews were being deported to concentration camps.

Mr Pankoke reasoned that, for Mr Van den Bergh to have that level of protection, he must have had some leverage with the Nazis. 

Pieter van Twisk, a veteran Dutch journalist from the team added: "Van den Bergh wasn't deported. And we went into the city archive and found proof that actually he was 'Aryanized,' so he lost his Jewish identity during the war. That was quite a feat. You couldn't just do that."

Mr Pankoke also showed CBS a note, which he said was received after the war by Ms Frank's father, Otto Frank. The message specifically names Mr Van den Bergh as the betrayer.

Mr Pankoke suggests anti-Semitism may be why Mr Frank never revealed his betrayer.

"He knew that Arnold van den Bergh was Jewish, and in this period after the war, antisemitism was still around," Mr Pankoke said.

"So perhaps he just felt that, 'If I bring this up again, with Arnold van den Bergh being Jewish, it'll only stoke the fires further'."

The team hopes that their work on the decades-old cold case will have an impact today.

"I think that people that are looking at this feel, 'Ah, maybe we can learn something if this case is solved,'" Mr Pankoke said.

"And maybe to the Holocaust survivors that are still out there, they understand that somebody still cares that these mysteries are solved."