Story highlights Mystery has persisted for 70 years over who betrayed Anne Frank

Police could have come to building to investigate another matter and found the Jewish families by chance

(CNN) Who betrayed Anne Frank?

It's a mystery that persists more than 70 years after police came to the Amsterdam building where Anne Frank and seven other inhabitants of the secret annex had been hiding.

The familiar story is that the police had been tipped off by an anonymous caller in a clear case of betrayal leading to the arrests on August 4, 1944.

But new research at the Anne Frank House re-evaluates that assumption.

Perhaps the Sicherheitsdienst or SD (German Security Service) didn't come to hunt for Jews that day, but inadvertently found the two families in hiding while investigating another matter.

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