Cleo was last seen at 1.30am on Saturday in a tent she was sleeping in with her parents at the Blowholes campsite in Macleod, north of Carnarvon.
“I urge anyone who has any knowledge of the location of Cleo, please provide that information to police and ensure that we can provide some certainty and information to Cleo’s loved ones,” Premier Mark McGowan said.
Mr McGowan said there were over 100 police personnel on the case as well as volunteers and Army reservists.
Police have taken hundreds of Crime Stoppers phone calls, primarily about suspicious people in the area.
“It is a sad situation and very difficult situation,” he said.
WA Police Deputy Commissioner Col Blanch said the $1 million reward was a “significant step” towards establishing where Cleo was.
It is the equal biggest reward ever put forward in WA.
Large rewards are historically offered decades, not days later, and usually in extreme cold cases, such as the disappearance of 12-year-old Lisa Mott in 1980, 28-year-old Lisa Govan in 1999 and the murder of 11-year-old Gerard Ross in 1997.
Mr Blanch said the government had approved the reward money as soon as police had requested it.
“The cooperation of the community is what we are urgently seeking,” the deputy commissioner said.
“Someone has the knowledge that can help.
“Now there’s a million reasons why you need to come forward.”
He assured the community police were doing everything they could.
“Despite an extensive land, sea and air search, we have not yet located her body. Her disappearance strikes at the heart of West Australians and I am here to provide assurance to the community that everything that can be done is being done,” he said.
“There has been a lot of anguish and there has been a huge outpouring of grief from the community. They have been doing it tough but are dedicated.”
Detective Superintendent Rod Wilde of the Major Crime Division said authorities were hopeful they would find Cleo alive.
“But we hold great fears for her safety,” he said.
Mr Wilde said police were led to believe the little girl had been taken from the campgrounds where she went missing from because of how many days the search had gone on.
“We imagine we would locate her given the amount of resources and the detailed search that is taken place, that leads us to believe that she was taken from there.”
Mr Wilde said police were not questioning any suspects yet.
The reward comes as the search for missing girl enters its sixth day.
Although efforts intensified over the last few days, with authorities even bringing in the the ADF to assist with the search, police say they still have no suspects in the disappearance.
Officers yesterday did reveal though that the zip to the tent she was sleeping in was left open higher than she could have reached.
Inspector Jon Munday said the position of the zip fully open at the entrance flap nearest to where the little girl was sleeping “is one of the circumstances that has caused us to have grave concerns for Cleo’s safety”.
The tent has been seized for forensic examination.
“The account given to us by Cleo’s parents, there’s nothing to indicate that that account is anything but accurate and truthful,” Inspector Munday said.
More than 20 registered sex offenders who live nearby have been spoken to by police, while authorities also try to track down all campers who may have been present at the time of Cleo’s disappearance.
Officers also say on their agenda is investigating reports of a screeching car around the time she went missing.
“We haven’t ruled it out or in,” Commander Darryl Gaunt said.
“It’s a little bit unsubstantiated.”
Little Cleo was last seen at 1.30am on Saturday when she woke her mother to ask for a drink of water.
She went back to sleep in her pink pyjamas shortly after. By morning, she and her sleeping bag had vanished.
The hours in between leave a five hour window, meaning by car she could have travelled as far north as Onslow, or Kalbarri in the south and edging towards Tom Price to the east.
Police say they will not stop searching the area where Cleo was last seen until they are “certain” she is not there.
Anyone with information is asked to call police immediately on 131 444. Callers are asked to provide the reference number CAD 781784.
The likelihood that Cleo was kidnapped while her parents slept has rocked their nearby hometown of Carnarvon.
Baker Joseph Nguyen one of the last people to see the hazel-eyed girl before her family ventured on their fateful camping trip.
“I gave her a biscuit just the day before she disappeared, so it was very heartbreaking when I heard the news,” Mr Nguyen said.
“I have two kids as well … that makes me really scared, really worried.”
Mr Nguyen is now feeding the frontline who are trying to find Cleo.
“That’s all we can do to help them out because I can’t go out looking for the girl.”
The town’s only sign-maker can’t churn out posters fast enough.
“There’s a lady, she’s running a page handing them out every few hours, she’s coming in for another 500,” Jace Kempton from Carnarvon Signworks said.
Mr Kempton said the community was “on edge as you can only imagine”.
“You can’t go anywhere without seeing something or hearing about it.
“Someone has to know something, someone has to slip up somewhere.”
The mum of missing four-year-old Cleo Smith has issued a new plea as the search for the little girl continues into a sixth day.
Ellie Smith posted a plea for her daughter’s return on her Instagram, asking anybody who knew anything about her disappearance to contact police.
“I miss you. I love you. Please come home to me,” read one.
“My sweet girl. Come home to me,” Ms Smith wrote in another.
“If anyone sees anything at all, please call the police.”