The Hague, Jan 18 : The Jewish family of Anne Frank hiding in Amsterdam during World War Two was most likely betrayed by a notary in Amsterdam, says a new cold case investigation.

The results were summed up in the book entitled "The Betrayal of Anne Frank. A Cold Case Investigation", written by Canadian author Rosemary Sullivan. It was published on Monday, reports Xinhua news agency.

The investigative team that had analysed the betrayal of Anne Frank and her family for years came to the conclusion that Jewish notary Arnold van den Bergh had given away their hiding place to the Nazi German occupiers in the Netherlands along with the addresses of others in hiding to save his own family.

No definitive proof was found, but according to the team Anne Frank's father Otto Frank, the only family member who survived the war, himself seemed to have taken the theory seriously.

Anne Frank, born on June 12, 1929, is one the most famous Jewish victims of the Holocaust during World War II.

Her diary has been published in several languages and adapted for stage and screen alike.

During the Nazi occupation of the Netherlands between 1940 and 1945, Anne Frank and her family went into hiding in Amsterdam in 1942 to escape persecution.

Two years later, the Franks were betrayed and Anne along with her elder sister Margot were transported first to Auschwitz and then to the Bergen-Belsen concentration camp, where they both died of typhus probably in February or March 1945.

The exact date of their death remains unknown.

Despite the extensive attention paid to Anne Frank's life since the first publications of her diary, up to now it was not clear how the Nazis discovered the Frank family's hiding place in a secret annex on the Prinsengracht in the centre of Amsterdam.

In 2016, Dutch filmmaker Thijs Bayens came up with the idea to study one of the best-known mysteries of the World War II with the help of modern police techniques and investigative tools.

A 23-strong team led by retired Federal Bureau of Investigations (FBI) agent Vince Pankoke collected interviews, diaries, address lists and war files from archives worldwide to test the existing and new hypotheses.

The investigators revisited a series of old suspicions and tested the theory that the discovery of the secret annex was merely a coincidence. Central to their investigation was an anonymous note that was delivered to Otto Frank shortly after the war.

Although the trail to the original was deadlocked, the team managed to find a copy of it made by Otto Frank in a police officer's family archives.

"At the time, your hiding place in Amsterdam was communicated to the Judische Auswanderung in Amsterdam, Euterpestraat, by A. van den Bergh, who at the time lived near Vondelpark, O. Nassaulaan. At the J.A. there was a whole list of addresses passed on by him," the note read.

Otto revealed the note's existence back in 1964. At the time, despite the note, Van den Bergh was not regarded as a suspect, because he himself would have been in a concentration camp in 1944 and so he could not possibly have given the address from there. This changed when the investigators found out that he had not been in a camp at all. This set them on the trail of Van den Bergh.

During the war, Van den Bergh did everything he could to prevent his own and his family's deportation.

As a prominent member of the Jewish Council, he was granted a postponement of deportation for a long time, and he arranged a hiding place for his daughters.

Later, he managed to convince the German officials that he was not Jewish and quit the council, but in 1944 he was again designated as Jewish. That was the moment when Van den Bergh decided to pass on the addresses of hiding Jews he had obtained during his time as a member of the Jewish Council to the Germans.

According to the researchers, questions still remain.

They will never know exactly how and why Van den Bergh, who died in 1950 of throat cancer, betrayed the Frank family.

Investigation sheds new light on Anne Frank's betrayal