The bone was sent to the state Medical Examiner's office in Chapel hill for further examination.
Zahra Clare Baker was reported missing Oct. 9, and authorities say they believe she is dead.
On Monday, investigators confirmed that a prosthetic leg found last week in Caldwell County belongs to the girl. The leg was found near a home where the child's stepmother, Elisa Baker, once lived.
On Wednesday morning, searchers returned to the area to drain a nearby pond.
Zahra and her father lived in Australia until he met a woman online and moved to North Carolina to marry her.
Elisa Baker, 42, remains in jail on an obstruction of justice charge. Police said she acknowledged to writing a bogus ransom note found at the scene of a fire in the family’s back yard on the day Zahra was reported missing.
The girl's father, Adam Baker, and Elisa Baker told police they had last seen Zahra in her bed at their home in Hickory on Oct. 9, but police don’t believe them.
Investigators said Zahra may have been alive when the family moved to a new home in North Carolina in mid-September, but they’ve had trouble finding anyone else who has seen her in recent months.
A mattress found by workers at a Caldwell County landfill last week is being tested for DNA evidence in the case, and investigators continue to search the family's home for other evidence.
Adam Baker insists he had nothing to do with Zahra’s disappearance, but police have not ruled him out as a suspect.
Eric Gein, who operates crime memorabilia website Serialkillersink.net, claims Elisa Baker has written him from jail. He is selling those letters on his website, WBTV reported Wednesday.
Gein says in one letter, Elisa Baker wrote of herself and her husband, "We didn't really kill her but what he did after the fact is kinda horrifying." She goes on to say she is afraid of her husband.
Hickory police could not confirm the authenticity of the letters.
Copyright 2023 by WRAL.com and the Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.