Strike Force Karabi investigators have discovered the mother-of-two's Facebook account was suspiciously deleted in the hours after she disappeared in Muswellbrook last September – and before she was formally reported missing to police.

The Newcastle Herald can reveal that detectives have also summoned the help of the formidable US Department of Justice to assist in gathering evidence about the accessibility of the account and who may have shut it down.

In the meantime, they have pleaded with anyone who may have been corresponding with Ms McBride to come forward.

"Obviously the timing [of the shutting down of the account] is fairly suspicious," Detective Sergeant Ian Wright said on Thursday.

"We want to speak to anyone who she may have been in contact with using Facebook, any dialogue that they may have shared."

The potential breakthrough comes just over 10 months after Ms McBride travelled from her Belmont home to Muswellbrook with her new boyfriend to visit one of her children at an ex-partner's house.

Her new boyfriend has told police he dropped Ms McBride off at the Calgaroo Avenue premises about 12.30pm, while her ex-partner said she left his house about 2pm to walk to nearby McDonald's.

Despite large land searches near the Ironbark Estate where she was last seen, police have come up almost empty-handed.

But they also revealed on Friday that they were looking into witness accounts that could place Ms McBride near the search sites on the day of her disappearance.

"There has been some possible sightings around the Muswellbrook area that day and we are doing everything we can to try and confirm those," Detective Sergeant Wright said.

With the end of national missing persons week on Friday, Ms McBride's devastated mother has penned a letter pleading for information, while directing some language to the killer.

"No one deserves this in life, but my baby is reeling you in. You are breaking while we are aching," Ms Williams wrote in the letter published below.

"Your truth is Carly's truth and, in turn, is our truth.

"Please someone speak up."

Ms McBride's father, Steve McBride, also repeated calls for people "who would know" to show a conscience and tell police.

"They can only keep things close to their chest for so long," Mr McBride said.

"It will only be a matter of time before someone reveals something in some way."

He attended the opening of missing persons week in Sydney in a bid to keep his daughter in the minds of the public.

"I have gone to the start of [national] missing persons week and I just so hope that I don't have to show up again next year," he said.

"I met a woman who has not seen her child since 1987 and we just could not bear that."

He said most of his family had lost hope of finding the 31-year-old alive, a reality he had attempted to come to grips with in the days after her disappearance.

"It was fairly obvious to me that would be the case from the outset," Mr McBride  said.

"It was not just your average missing persons case.

"One thing I guess in Carly's case is that her disappearance came as a great sadness rather than a great shock to me.

"Unfortunately, Carly had been having some difficult times in her life and I was sort of expecting trouble of some kind, so it didn't come as such a shock that something happened.

"I obviously wasn't expecting something as horrible as this."

But her family is desperate to find not only what happened to Ms McBride, but where she is.

It is critical for them as they continue to grieve.

"I think as important as finding her is, somebody also needs to be held accountable for this," Mr McBride said.

"For me, I know Carly is gone and nothing can bring her back.

"But if she can be returned then it would be terrific.

"When the case wasn't immediately solved, I definitely readied myself for the fact that it might not be.

"But something tells me that it will be solved.

"These detectives are not letting up, they have been so intense with the investigation, that I think they will eventually find out what happened to Carly.

"We need a final resting place for Carly to give us somewhere to go and grieve."

Close friend and flatmate Kylie Smith said nothing appeared out of the ordinary as she spoke with Carly on the phone as she travelled to Muswellbrook.

Her group of friends remain gutted at not knowing her fate.

"She was so down to earth. I would call her a free spirit, she was easy going, she just loved life," Ms Smith said.

"She was always there for her friends; if you were having a bad day she just knew and she would be in contact.

"You spend your whole life searching for a friend like that and now I have lost one, you just can't get over that.

And she also made a plea.

"We all wake every day not knowing what happened, not knowing where she is," she said. "You have to have a conscience, come forward with some news, just give us something."

Despite several large land searches in areas around  where Ms McBride went missing, police have not unearthed much evidence.

Police have also pleaded with anyone who may have been giving information to the Help Find Carly McBride Last Seen In The Hunter Facebook site to also contact police.

A letter from Lorraine Williams, mother of Carly McBride

I DON'T believe there is one person who does not now know what happened to my bub or hasn't noticed what has happened on that fateful day.

Please help us for her children, they are innocent and gorgeous babies.

Whoever you are, you have taken their mummy away, their lifeline to fun times and happiness in their lives. Their tower of strength.

They will never feel her soft, warm and reassuring kisses and her big, warm hugs with that big, contagious belly laugh of hers and her radiant smile.

Their memories are lost, they can not say goodbye to her.

Our pain, anguish, angst and frustration are keeping us all down, causing us to wake up super vigilant that we might get a call to say they have found my bub.

Whoever you are, you decided on that day to rip my daughter away from us, you bottom feeding runt.

We are left with question after question after question.

We don't know how to grieve or what we are grieving, we are in a kind of grief limbo.

Our little, beautiful poor babies need to know where their mummy is.

They are the innocent victims in this horrible nightmare we are enduring.

Please someone come forward so they can move on and grow into the amazing people their mummy would have wanted them to be.

We can't honour and respect Carly's life until she is found.

My daughter is reeling you in and you will be a fine catch when you least expect it.

This is my only wish, that we find my bub, that we can put her to rest; it is a basic human right with the dignity and respect that she deserves.

Then her babies, and their beautiful but broken hearts and heads, can start to heal and they may have a life without the anguish and pain and angst.

You didn't give my daughter a chance, please give her children the knowledge they ache for.

William and Kaydence should not be burdened with this pain.

Please help us give them some semblance of grief and loss in their journey.

Carly is a proud Aboriginal woman, as is her beautiful sister, and I am proud and honoured to be their mother.

No one deserves this in life, but my baby is reeling you in. You are breaking while we are aching.

Your truth is Carly's truth and, in turn, is our truth.

Please someone speak up.

Newcastle Herald