Top cop in Madeleine McCann case reveals the 'real complication' in Cleo Smith's disappearance as worrying new clue suggests the four-year-old WAS abducted - but there are STILL no suspects

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A top detective who investigated the abduction of British toddler Madeleine McCann has weighed in on the eerily similar disappearance of Cleo Smith, who hasn't been seen since she vanished from a remote campsite in Western Australia.

The four-year-old girl, wearing pink pyjamas, was last seen by her parents at about 1.30am on Saturday in the family's tent at the Blowholes camping grounds near Carnarvon on the remote north-west coast.

By the time her mother Ellie Smith and step father Jake Gliddon woke up at about 6:30am, she was nowhere to be found - with the tent zip leaving the entrance open.

It has since emerged that the little girl wouldn't have been tall enough to open the zip herself with police now focusing on the grim possibility that she was abducted, although there are still no suspects. 

But while there are 'grave fears' she was snatched, investigators are not ruling out the possibility she wandered off alone, with a massive land, sea and air search across the area entering its sixth day on Thursday as homicide detectives and missing persons specialists continue to scour the scene.

But UK cop Dr Graham Hill, who flew to Portugal to help in the desperate hunt for three-year-old Madeleine back in 2007, said there is one 'real complication' which suggests Cleo did not just wander off - the fact that her red and grey adult-sized sleeping bag is also missing. 

The search for Cleo Smith (pictured) is now entering its sixth day, with police not ruling out any scenarios - but also not identifying any potential suspects 

The adult-sized sleeping bag Cleo was sleeping in has also disappeared, police confirmed

'I would say it's a remote chance that she's got up, wandered off and taken her sleeping bag with her. I think that's highly unlikely because there'd be some disturbance. You'd see where she dragged the sleeping bag and how far is a four- year-old child going to get in the dark?' he told the West Australian.

The disturbing worst-case scenario is backed up by a worrying new development revealed by police on Wednesday night.

WA Police Inspector Jon Munday said little Cleo was too short to reach the zipper of the tent entrance, which was found hanging open by her mother at 6.30am.

He said the height of the zip opening on the tent was a major piece of evidence that could point to the possibility Cleo has been deliberately taken from the tent while her parents slept. 

'The positioning of that zipper for the flap is one of the circumstances which has caused us to have grave concerns for Cleo's safety,' he said. 

'There are circumstances around her disappearance that make it very concerning ... like the fact that the zipper was allegedly up so high (and) the sleeping bag is missing.'

Police have revealed little Cleo (pictured with mother Ellie Smith) was too small in stature to reach the zipper of the tent entrance, which was found hanging open by her mother

Police roped off the area where Cleo vanished from her tent (pictured) in the middle of the night as they continue to investigate her disappearance 

Madeleine McCann (pictured) went missing in Portugal during a family holiday in 2007, with a child abduction expert who flew to Praia da Luz to help saying Cleo's disappearance had 'real complications' because of her missing sleeping bag 

The family tent had several entry points that could be unzipped, with the one found open being at the front-facing area of the tent where the little girl had been sleeping. 

Dr Hill – then a Surrey detective superintendent seconded to the UK’s new Child Exploitation and Online Protection centre – lent expert help to the hunt for Madeleine back in 2007.

An expert in the abduction and murder of children by sexual predators, he told her father Gerry that if Madeleine had been abducted - she would likely be dead.

In the majority of cases where a child is taken by a stranger, they are usually killed within three to six hours, with Dr Hill admitting 'the statistics don't lie'. 

Other campers claim they heard the sound of a car speeding off around 3am, with police revealing up to 20 sex offenders live near the campsite where Cleo was last seen five days ago.

Investigators have disclosed that while there are currently no concrete suspects for Cleo's disappearance, there are 'groups they are interested in'.  

The startling zipper development means that if Cleo was abducted, an intruder would have had to have crept into the family tent in the middle of the night and taken her, along with her sleeping bag, without waking anyone up.

Dr Hill said it's vital for investigators to know who was near the campsite that evening - as a potential abductor would have noticed Cleo and decided to pounce.

'When people abduct children, they have to see them in the first place. They have to know that they exist.  So if that little girl turned up at the campsite late last Friday. Was she running around whilst they put the tent up?' he said.

The four-year-old was last seen by her parents (pictured with her mum Ellie and partner Jake Gliddon) about 1.30am on Saturday when she woke up and asked for a drink

Cleo Smith woke up in the middle of the night and asked her parents for a sip of water hours before she disappeared 

'Offenders only abduct children they know exist. They don't wander around people's tents at night in the hope they're going to bump into a little child.'

As each hour passes the situation grows more and more concerning for Cleo. 

Her shell-shocked parents fronted the media for the first time on Tuesday fighting back tears as they made a public appeal for information.

When Ellie Smith first realised her 'delicate and funny' daughter was missing from their family tent before the sun had even risen, she made a beeline for her old favourite spots to play. 

Dr Graham Hill is an expert in the abduction and murder of children by sexual predators, and assisted on the Madeleine McCann case. He said if Cleo has been taken, it is likely by someone who had noticed her at the campsite earlier in the day

Ellie Smith and her partner, Jake Gliddon (pictured) fronted the media for the first time on Tuesday after four-year-old Cleo (middle) went missing near the Blowholes campsite north of Carnarvon in Western Australia five days ago

The mother-of-two has been visiting the Blowholes camping ground since she was a child and immediately thought to go 'everywhere we went as kids'.

It would be at least another three hours before she alerted police, who arrived on the scene 'mid-morning Saturday'. 

She hoped to find Cleo hiding out somewhere, although she knew it was unlikely.

'[Cleo] would never leave us. She would never leave that tent alone... She's lazy when it comes to walking,' Ms Smith said on Tuesday.

If Cleo needed anything, Ms Smith is certain she would have woken her up rather than wander out of the tent alone, just as she did when she wanted a sip of water earlier in the night. 

Cleo's stepdad Jake Gliddon was frantic, according to a camper on the scene who assisted with the search

Pictured: A timeline of Cleo's holiday with her family, from before she disappeared to the present search

Emergency services and police have been scouring shacks near the scene for five days

Cleo's stepdad Jake Gliddon was frantic, according to a camper on the scene who assisted with the search.

Mr Gliddon started dating Ms Smith two-and-a-half years ago, when Cleo was barely one. 

It's understood he has raised Cleo as his own ever since.

'You are incredible and the best dad Cleo could ask for,' Ms Smith said in a tribute post to her partner last Father's Day.

'Thank you for stepping up and being her Daddy. We love you... our favourite man.' 

A close friend of the couple said Mr Gliddon 'absolutely adores Cleo [and] took her on as his own not long after she was born'.

'He may be a stepfather but those kids mean the world to him... He's a great dad.' 

A close friend of the couple said Mr Gliddon 'absolutely adores Cleo [and] took her on as his own not long after she was born'

A number of touching new photos of Cleo (left) with her family, including mother Ellie (centre) and baby sister Isla (right) have emerged showing a cuddly, affectionate little girl

Police have not ruled out any possibilities and continue to search the scene (pictured, checking a shack at the Blowholes campsite)

Cleo's parents last laid eyes on her at 1.30am on Saturday, hours after they arrived at the campsite about 6.30pm on Friday. 

She'd been sound asleep but woke up to ask for a sip of water. Her mum tucked her back in her red and grey sleeping bag and went back to sleep herself.

Four-and-a-half hours later, she was woken again by seven-month-old Isla, Cleo's sister and Mr Gliddon's biological daughter. Cleo was gone.  

Ms Smith and Mr Gliddon immediately alerted all other campers in the vicinity.

Some of the guests sent up privately owned drones to search for Cleo from the sky, while others were on motorbikes scouring the area.

Her mum and stepdad, meanwhile, searched high and low. 

'We went looking, checking, making sure she wasn't around the tent, and then we got in the car and started driving around everywhere,' Ms Smith said. 

Friends of Cleo's family said the smart four-year-old (pictured) 'wouldn't just wander' away from the tent

Pictured: The tent where Cleo disappeared from in the early hours of Saturday

'We literally grew up probably like 100m from literally where our tent was — that was where we stayed at the same age, so we just looked everywhere that we went as kids and we couldn't find her,' she said.

It was only after this that the couple 'realised we have to call the cops because she's not here'.     

By the time detectives arrived, the ground search was well underway. 

'The mother and stepfather were absolutely distraught,' one of the fellow campers said.

The woman claimed all tin sheds at the site were opened and searched, but that the camp ground wasn't closed 'for hours' after police arrived.

New campers were permitted to arrive well into Saturday morning, while many more left.

Mr Gliddon started dating Ms Smith two-and-a-half years ago, when Cleo was barely one. It's understood he has raised Cleo as his own ever since

Cleo vanished from the Blowholes campground near Carnarvon, on WA's remote northwest coast, in the early hours of Saturday morning

After police arrived, the camper said they were 'very thorough in taking everyone's details who left the site before it was officially closed'. 

Police have not ruled out any theories relating to Cleo's disappearance - including the possibility that she was abducted. 

Cleo's mum noted the four-year-old was 'terrified of the ocean' and wouldn't wander into the water, but that she was excited about building sandcastles on the beach.

She was also preparing to learn to ride her bike without training wheels.   

As the search enters its fifth day, there are mounting concerns Cleo could be anywhere - including potentially interstate.  

'We can't rule out the fact that Cleo may be still in the area, we can't rule out the fact she's left the area and if she's left the area that is probably is our worst case scenario because that really paints a sinister picture with what's happened,' Inspector Jon Munday said.

'It is a race against time. We're just trying to find answers.' 

Cleo Smith (left) with her mother Ellie, her partner Jake Gliddon and her baby sister Isla (right)

Cleo's mother Ellie Smith revealed yesterday that Cleo had been sleeping in a separate area of the tent, with her baby sister Isla just metres away

Mr Munday vowed to continue 'throwing everything at this' for as long as it takes to bring Cleo home. 

Police have also identified up to 20 sex offenders who live near the campsite where she was last seen five days ago. 

In a radio interview on Wednesday, Assistant WA Police Commissioner Darryl Gaunt said detectives have been making inquiries about all known sex offenders' whereabouts but do not believe any were involved in Cleo's disappearance.

The camp ground is located 75km from Carnarvon and 875km from Perth with nothing but bushland and scrubs in between. 

Cleo's biological father Daniel Staines voluntarily spoke with police at Mandurah Police Station on Monday in relation to his daughter's disappearance.

He was 1,000km away at the time and is not considered a suspect.

It's not clear what relationship he and Cleo had, particularly given Ms Smith referred to her new boyfriend as Cleo's dad.

Mr Staines is yet to comment publicly on her disappearance.

Police say they have grave concerns for the child (pictured) and that 'everything is on the table' in the unusual and disturbing case

Body language expert reveals Cleo's mum and stepdad are struggling to hold it together

The mother and step-father of missing four-year-old Cleo Smith are experiencing 'genuine sadness' as they struggle to keep it together, body language experts have revealed.

When Ms Smith and Mr Gliddon fronted the media on Tuesday,  they appeared emotional and 'lost for words'. 

'In the cases similar to this that I've worked on I've seen much more emotion from both parents. I think she's working hard to keep it together,' body language expert Traci Brown told Daily Mail Australia.

'I heard her voice waiver a bit and that's the only way I could tell real sadness is there. I think his stress response is to shut down so that's what we're seeing.' 

She added the couple appeared to be 'wired differently' in terms of emotional responses, pointing out Mr Gliddon gave off a 'heavy energy' despite appearing stiff and less reactive. 

'My guess is he's the strong silent type,' Ms Brown said.   

Both had their arms crossed, which was a sign the pair were facing 'stress triggers' as the pair exhibited 'self-comforting behaviour' during the interview.   

Body language experts have weighed in on the interview analysing the gestures, tone of voice and facial expressions of the couple