Acting Superintendent Evan Quarmby says he can't confirm that the bones - which include a skull - are those of a woman but it does appear that they are.
"The very early indications at this stage, which cannot be confirmed until after the results of the post-mortem, is that the remains appear at this stage to be female," he told reporters outside Bowral police station, near the forest in the NSW southern highlands.
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"However, we don't have any further details on that and can't be drawn on that further until after the results of the post-mortem."
The Belanglo forest was the killing ground for the notorious serial killer Ivan Milat, who partly buried seven young victims there in the early 1990s.
An autopsy on the remains would begin on Wednesday, Superintendent Quarmby said.
The results would not be known until after the investigation at the crime scene had concluded.
He said numerous items had been collected from the area where the remains were discovered and other items had been collected from "around the general area".
The bones were found by trail bike riders next to a fire trail on Sunday.
Superintendent Quarmby would not say what the other items found by police were.
He said there was no further indication about how old the person was at the time of death, or how long the remains had been in the forest.
A hugely detailed search was now under way at the scene, including line searches and specialist officers sifting through soil "grain by grain".
Police would be present in the forest for as long as necessary for the investigation, Supt Quarmby said, without giving any potential time scale.
"The expanded search area at this stage continues to expand," he said.
"We started obviously at the actual crime scene and are working in increasing circles out to ensure we cover everything we possibly can."
Homicide detectives had taken the lead on the investigation because they had the resources and expertise to best deal with case, Superintendent Quarmby.
He refused to comment on any possible links with Milat.
