One of World War II's most enduring mysteries may have been solved after a cold-case investigation identified a Jewish notary as the prime suspect in the betrayal of diarist Anne Frank and her family.
The evidence comes from modern data-crunching techniques combined with a long-lost, anonymous note sent to Anne's father Otto naming Van den Bergh, according to a new book about the investigation.
The Anne Frank House museum said it was "impressed" by the evidence in the book being published on Tuesday by Canadian author Rosemary Sullivan, but that further investigation was needed.
Theories have long swirled about the Nazi raid on August 4, 1944, that uncovered the secret annexe to an Amsterdam canalside house where Anne and her family hid for two years.
Retired FBI detective Vince Pankoke was enlisted by a Dutch documentary-maker in 2016 to head a team to crack the "cold case" that two previous police probes had failed to.
"This was frozen," Pankoke, who had previously investigated Colombian drug cartels, told the CBS "60 Minutes" show.
The name of Van den Bergh, who died in 1950 of throat cancer, had previously received little attention.
But it rose to the top of a list of four suspects during Pankoke's investigation, which used modern techniques including algorithms to find new links in troves of information, and employed experts in various fields.
Van den Bergh was a founding member of the Jewish Council, an administrative body that the Nazis forced Jews to establish to organise deportations from the Netherlands.
Investigators found he had initially managed to get his family exempted from being transported. But this was revoked around the time of the raid on the Franks, leading them to suspect he may have betrayed their hiding place to save his own children.
He would also have had the opportunity to pass on the information, as he had been the notary for a German art dealer's sale of a collection of looted Jewish art to senior Nazi Hermann Goering.
But the most convincing element for the investigators was the seriousness with which Otto Frank treated the allegation.
Anne's father told detectives in 1964 that he had received a note shortly after the war naming Van den Bergh as the betrayer of his family, and of several other people. A copy made by Frank of the note was found by the team in a police officer's archives.
The team discounted some 30 other theories, such as a long-running suspicion that it was linked to black market activity, or just a coincidence, the investigators said.
"We do not have a smoking gun, but we do have a hot weapon with empty casings next to it," Pankoke was quoted as saying by Dutch public broadcaster NOS.
The findings, published in full in Rosemary Sullivan's book "The Betrayal of Anne Frank", are already provoking soul-searching in the Netherlands.
Ronald Leopold, executive director of the Anne Frank House, told AFP that the probe had "generated important new information".
But he said that questions remained, in particular about who had sent the anonymous note, and why.
"You have to be very careful about sending someone down in history as a traitor to Anne Frank if you are not 100 or 200 percent sure about that," he added.
Investigators believed Otto Frank may not have publicised the note for fear that the discovery a Jewish person was behind the betrayal could have stoked further anti-Semitism.
Thijs Bayens, the Dutch film-maker behind the project, told 60 Minutes that the aim was not to demonise the betrayer, since it was the Nazis who had after all "brought people to do these terrible things"."The real question is: what would I have done?" he said.