"There was a dark side." What Michael Jackson's maid witnessed at the Neverland ranch.

Michael Jackson’s former maid, Adrian McManus, has opened up about her experience working for the late pop star.

The 56-year-old began working for Jackson in 1990 and soon became responsible for cleaning his bedroom at the Neverland Ranch.

She will detail her experience working for Jackson during an exclusive interview with 60 Minutes’ Liam Bartlett this Sunday night.

“Three months after I started working there, the girl that was cleaning his bedroom left suddenly,” she tells Bartlett.

“Nobody knew why. And I was told I was going to have to clean his bedroom.”

Watch the preview for Adrian McManus’ chilling interview on 60 Minutes.

McManus says as she became privy to Jackson’s private domain, she saw scenes which she believes confirm his predatory behaviour towards children.

“The first time I cleaned his bedroom, I didn’t even know where to start,” she says.

“I saw a lot of fondling. Him rubbing his hands in kids’ hair, kissing them.

“I started realising, thinking, wondering, when he was taking baths with them, and they were sleeping in his bed.”

She also specifies she would often find several pots of Vaseline on the property.

“There was a lot of Vaseline in Michael’s bedroom. It was actually all over [Neverland] ranch,” she says.

“Sometimes it was found in the golf carts when Mr Jackson would take off with the with the boys.”

McManus' accusations come after a recent HBO documentary, Leaving Neverland, shared the testimony of his alleged child sexual abuse victims.

Wade Robson, 36, and James Safechuck, 42, said they met the singer at the ages of seven and 10 respectively, and both claimed Jackson groomed them, before sexually abusing them at Neverland Ranch.

Despite this, during his life Jackson was never formally charged for his crimes. In 1993, Jackson was investigated by the Los Angeles Police Department after he was accused of abusing 13-year-old Jordan Chandler. In the same year, Chandler's parents also filed a civil lawsuit against Jackson, accusing him of sexual battery, battery, seduction, wilful misconduct, intentional infliction of emotional distress, fraud and negligence.

However, Jackson was never indicted for these accusations and he settled his civil suit with the Chandler family for $22 million USD ($30.8 million AUD).

As for why McManus is only sharing her side of the story now - 10 years after the King of Pop's death in 2009 - the former maid says at the time she felt threatened for her life.

“I was scared to say anything bad about Mr Jackson,” she says.

“I was threatened that they could hire a hitman to take me out, slice my neck, wouldn’t ever find my body.”

60 Minutes airs tonight after Married at First Sight on Channel Nine at 8:30pm.

Read more on this topic:

Without us noticing, it looks like Michael Jackson groomed us for decades.

The signs Michael Jackson was grooming the children he was close to that so many missed.

"It wasn't going to mean anything": Why Michael Jackson married Lisa Marie Presley.

'Blanket' Jackson was just seven when his father died. This week he stopped talking.

The two boys who followed Wade Robson into Michael Jackson's bed insist they weren't abused.

Debbie Rowe says she gifted Michael Jackson two children because he was a 'wonderful man'.