Investigator reveals the first words of Josef Fritzl's daughter after 24 years of torture.

An investigator involved in the 2008 rescue of Josef Fritzl’s daughter has revealed the first words the Austrian woman uttered to police when she was freed from her father’s bunker.

In a documentary for UK network Channel 5 titled Fritzl: What happened next, Willibald Reitner of Amstetten police said when he interviewed Elisabeth Fritzl she revealed nothing at first, saying, “No one will believe me anyway”.

“Then we changed our tack and we told (her), ‘Well, maybe you are the victim?’ Suddenly Elisabeth had a different expression about her,” Reitner said, according to The Mirror.

“After that she said, ‘If I tell this exactly how it all happened, no one will ever believe me’.”

After laying down conditions – including that she would never have to see her father again – she told her story, a story that would unravel into one of the most infamous sex crime cases of the 21st century.

Catch the latest episode of Mamamia’s True Crime podcast. Post continues…

Since the age of 18, Elisabeth had been trapped in a locked, sound-proof basement beneath her parents’ home. There, in cramped living quarters with little more than a small bathroom and bed, she was held by her father as a prisoner and sex slave for 24 years.

In that time, Fritzl drugged her, raped her over 3000 times and fathered her seven children.

To her mother, Rosemarie, and to the rest of the outside world, Elisabeth had simply run away to join a religious sect; a smokescreen created by Fritzl that no one managed to see beyond.

It wasn't until April 2008 that the truth became clear.

The three children being raised by Fritzl and his wife had not, as he claimed, been left on their doorstep by Elisabeth.

They had been born right below them, in the cellar where their three siblings, aged five to 19, still lived, and where another had died.

When the eldest fell seriously ill, Fritzl relented to Elisabeth's demands and took the 19-year-old to hospital - her first time in the outside world, in sunlight.

Doctors, immediately suspicious about the teenager's condition, contacted police.

In March 2009, Fritzl was jailed for life after pleading guilty to murder by negligence, over the death of the baby he later incinerated, as well as enslavement, incest, rape, coercion and false imprisonment.

Now 82, he is held in a facility for "mentally abnormal criminals" at Austria's Stein prison.

Elisabeth Fritzl, aged 51, and her six children moved to northern Austria under new identities.

She has never spoken publicly about her ordeal.