Shayla Phillips was last seen about 2.30pm on Wednesday near Stormlea Rd in Stormlea, wearing pink leggings, a cream top, and gumboots.
Police say she had been playing outside with dogs from a neighbouring property. When her mother went to check on her after about half an hour, Shayla and the dogs were gone.
One of the dogs was found about 7pm on Wednesday about 800 metres from where Shayla was last seen.
Inspector Gavin Hallett said crews were still expecting to find the four-year-old alive.
"This is still a search and rescue operation," he told reporters on Friday.
"My grave concern is that she may be injured in the bush. She's four years old so she won't present to us.
"We actually have to find Shayla. She could be disorientated, she should be confused, she could be scared and she won't approach us so that's where our concerns are."
Insp Hallett said police did not believe there was anything suspicious about the disappearance and there was no person of interest.
The inspector said Shayla's mother Bianca remained stoic and strong.
"She, like us, holds grave concerns for Shayla, but she knows that we're doing everything we can to safely locate her as soon as we can," he said.
Assistant Commissioner Jonathan Higgins said significant resources, including thermal imaging drones and sniffer dogs from Victoria Police, were involved in Friday's operation.
"Tasmania Police are doing everything we possibly can to bring little Shayla back safely to her mum," Mr Higgins told reporters on Friday.
"We absolutely need to be positive there'll be a good outcome. But we will continually reassess as well and take advice from the medicos and experts."
Mr Higgins said Tasmania Police were consulting with other states following a number of successful child rescues in the past few years.
"We do reach out and speak about their experience with people they've been looking for and certainly techniques and resources they might use to actually get successful outcomes," he said.
The Phillips' family home is in an isolated area, surrounded by undulating pastures and dense bushland.
The helicopter is searching an area of about 2.5 square kilometres, while search teams are covering an area of about 1.2 sq km on foot.
Four nearby dams were searched and cleared on Wednesday night.
Insp Hallett said crews would continue to search through the night and into Saturday if Shayla was still not located.
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