The Madeleine McCann investigation stalled for years. Then police found eight buried hard drives.

Madeleine McCann would have turned 22 next week.

Instead, her family remain locked in a desperate search for answers over what happened to the toddler when she disappeared from a resort in Praia da Luz, Portugal, on May 3, 2007.

A new investigative documentary, Maddie: The Unseen Evidence, from UK newspaper The Sun, claims to reveal a series of evidence that police have reportedly been sitting on since 2016. They allege it reveals Madeleine's fate.

The documentary is a look into what authorities have on Christian Brueckner, a convicted rapist, who is suspected of kidnapping the three-year-old from the Algarve holiday apartment complex.

This reportedly includes a hard drive containing photographs German authorities believe indicate that Madeleine is no longer alive.

Brueckner has continued to maintain his innocence.

Listen to The Quicky discuss the new probe into Madeleine McCann's disappearance. Post continues below.

Madeleine McCann vanished from her family's holiday apartment on May 3, 2007. Image: Supplied.

The evidence in question was reportedly found at a disused factory owned by Brueckner in 2016. The newspaper says he bought the Neuwegersleben property for £20,000 ($41,358 AUD) in 2008, a year after Madeleine vanished.

Per reports, police were alerted to the site by a dog in 2016 and later discovered Brueckner's dead dog, buried alongside a wallet with six USB sticks and two memory cards containing concerning material.

One hard drive was described by police as 'deeply disturbing', according to The Times.

The search allegedly uncovered further items of concern, including children's clothes, as many as 75 children's swimming costumes, toys, masks, unlicensed weapons and ammunition, as well as bikes.

Listen to The Quicky discuss the latest development in this case. Post continues below.

The Sun also claims that police found Brueckner's writings detailing child kidnappings and photographs depicting child abuse.

Brueckner is a convicted rapist with a history of sexual abuse against both adults and children.

He was first charged with committing a sexual offence against a child in 1993, and was extradited from Portugal to Germany in 2017, serving 17 months for child sexual abuse.

He was later found guilty of raping a 72-year-old woman in 2005, and was sentenced to seven years in jail in 2019.

He is due for release in September 2025.

Christian Brueckner is the prime suspect in Madeleine McCann's disappearance. Image: Getty/Alexander Koerner.

Madeleine vanished from her family's holiday apartment on May 3, 2007. She was left alone with her twin two-year-old siblings, as their parents, Kate and Gerry McCann, dined at a nearby restaurant.

The McCanns were initially considered suspects in their daughter's disappearance, but were later cleared of wrongdoing.

No-one has ever been charged over the toddler's disappearance, but in June 2020, German authorities named Brueckner as the primary suspect in the case.

During a 2020 CNN interview, Braunschweig Public Prosecutor's Office prosecutor, Hans Christian Wolters, said authorities "actually have findings that suggest that he is Madeleine McCann's murderer."

He added that investigators had "insufficient evidence to convict".

Brueckner continues to deny any involvement in Madeleine's disappearance.

Feature image: Supplied.