Volunteers and emergency services have joined forces as they try to locate Sharon Granites who disappeared from her home near Alice Springs on the weekend.
A manhunt is also under way for Jefferson Lewis, 47, who was staying at Sharon's Old Timers Aboriginal town camp residence and went missing at the same time she disappeared, according to police.
Mr Lewis had been recently released from prison and had a history of assault and domestic violence charges, Acting Commander Mark Grieve said on Monday.
Northern Territory Police told AAP the search area had been expanded to 20 square kilometres on Tuesday, radiating outwards from the town camp.
Police and volunteers are searching shoulder-to-shoulder through dense buffel grass.
Around 60 people are involved in the search on the ground, with helicopters, drones, dog units, horses, motorcycles and all-terrain vehicles also deployed.
A specialised infantry regiment of the Australian Army Reserve is also assisting.
The local Tangentyere Council has also been coordinating community volunteers, who have streamed in to join the search.
The little girl was last seen by her family when she was taken to bed about 11.30pm on Saturday.
She was reported missing about two hours later.
Northern Territory senator Jacinta Nampijinpa Price backed police's calls for the outback community to come forward with any information they had to help find Sharon.
"This is every parent's worst nightmare," she posted on Facebook, saying her thoughts were with the family.
"Police have now issued an updated call for information, confirming extensive searches have been conducted but she has still not been located.
"If you know anything - no matter how small - please come forward ... let's help bring her home."
Mr Lewis was not in prison for child-related offending before being released but had a history of assault and domestic violence charges, Mr Grieve said.
"If he is involved, we certainly hope that no harm has come to Sharon," he said.
"Obviously, it's a terrible situation to have such a young child go missing.
"We want to find Sharon healthy and we want to get her back to her family."
Major Crime Squad detectives from Darwin have flown in to Alice Springs to investigate as the search for the little girl continued.
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