The search entered its third day on Tuesday after Sharon Granites was reported missing from Old Timers Aboriginal town camp near Alice Springs on Saturday night.
Police believe she was taken by Jefferson Lewis, 47, who was staying at the same property as Sharon and went missing at the time she disappeared.
Mr Lewis was recently released from prison and has a history of assault and domestic violence charges.
Around 70 volunteers were assisting police, emergency services and defence personnel in the search across a wide area on Tuesday.
Helicopters, drones, dog units, horses, motorcycles and all-terrain vehicles have been deployed in the search, as well as a specialised infantry regiment of the Australian Army Reserve.
Aboriginal trackers were also being used, Assistant Commissioner Peter Malley told reporters in Alice Springs on Tuesday.
The local Tangentyere council has also been co-ordinating community volunteers.
Police did not believe Mr Lewis had access to a vehicle or had left the territory, he said.
There had been a party at Old Timers Aboriginal town camp on Saturday night and police had attended but no offences had been detected.
Alcohol was consumed and Mr Lewis was probably under the influence of alcohol on Saturday night, Mr Malley said.
Police did not have a motive at this stage as to why Mr Lewis may have taken Sharon, he said.
"Our number one mission is to find her safe and well."
But as time went on, the chances of finding the girl alive are reduced, Mr Malley said, which was why so many resources were being put into the search.
Sharon's mother was distraught and police were providing ongoing support to her and the wider family.
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.
Northern Territory senator Jacinta Nampijinpa Price backed police 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."
Major Crime Squad detectives from Darwin have flown in to Alice Springs to investigate as the search for the little girl continued.
