AMSTERDAM • Hiding from the Gestapo secret police in an annex of her father's warehouse in Amsterdam during World War II, Anne Frank heard a little knock on the wall.
She could not be sure who or what it was and it frightened her.
She was right to be scared: Just months later, on Aug 4, 1944, the police discovered the hideout during a raid and arrested her and seven others living behind a movable bookcase.
All but Mr Otto Frank, the diarist's father and later the editor of The Diary Of A Young Girl, perished in Nazi death camps.
Anne Frank died of typhus at 15 in the Bergen-Belsen concentration camp in March 1945, just a few weeks before British troops liberated the place.
Who gave the eight people up has remained a mystery.
Now, almost 75 years later, a team of experts led by a retired Federal Bureau Of Investigation agent is turning to modern forensic science and criminology in hopes of solving one of history's most famous cold case files, reported the New York Times.
"We will put special emphasis on new leads," said the retired agent, Mr Vince Pankoke, 59.
"We need to verify stories as they come in, and we know that is going to lead to further investigation."
In the search for new leads, he and his team are digitally combing through millions of pages of scanned material from the National Archives in Washington as well as archives in the Netherlands, Germany and Israel.
The use of other modern techniques such as forensic accounting, crowdsourcing, behavioural science and testimonial reconstruction may also hold promise of a breakthrough.
The team, for example, is carrying out a three-dimensional scan of the original house and using computer models to determine how far sounds might have travelled.
Those techniques may allow them to re-evaluate old evidence - for instance, whether the knock on the wall, described in Anne Frank's diary, was someone telling those who were hiding that they were being too loud or whether it could have been a trap.
"We don't know what happened exactly on that fateful day and there is something intriguing about an open end in a narrative," said Mr Ronald Leopold, executive director of the Anne Frank House foundation, which runs a museum in Amsterdam and conducts research into her life and death.
Researchers in the Netherlands have welcomed the new investigation. "What is new about this one is that it looks at the case with forensic eyes," Mr Leopold said.
"And we look forward to the results."
Meanwhile, the Anne Frank Foundation has taken aim at a plan by Germany's national rail provider to name a train after her, saying the move "caused new pain" to those who experienced deportations to concentration camps.
"A combination of Anne Frank and a train conjures up the image of persecution of Jews and deportations during World War II," the foundation said in a statement.
The Guardian reported that the Deutsche Bahn rail company had wanted a name that its new high-speed trains could pay homage to.
Out of 19,000 suggestions, a shortlist of 25 names was drawn up, with the jury settling for Anne Frank.
In response to the controversy thrown up, the Deutsche Bahn said the naming exercise was "in no way intended to damage the memory of Anne Frank". "Rather, the DB, conscious of its historical responsibility, decided to keep the name of Anne Frank alive," it added in a statement.
Still, the company will "take seriously the concern currently expressed by the public and will hold internal discussions, with the blessing of Jewish organisations", it said.