North Carolina authorities confirm the prosthetic leg found last week was that of missing 10-year-old Zahra Baker.

The Hickory Police Department said in a written statement that "medical records obtained from Australia where the prosthetic leg was originally fitted matched the serial number on the leg."

Police found the prosthetic leg last Tuesday in an area where the girl's stepmother, Elisa Baker, used to live.

Zahra, a bone cancer survivor who used a prosthetic leg and hearing aids, was reported missing by her father, Adam Baker, on Oct. 9, a few hours after authorities responded to a fire in the Bakers' backyard. Authorities believe the girl is dead. 

Police said Elisa Baker, 42, confessed to writing a fake ransom note that was found at the scene of the fire on the same day her stepdaughter was reported missing. She has been charged with felony obstruction of justice. A Catawba County grand jury indicted her on the charge on Monday.

Zahra's father, meanwhile, was freed from jail last Thursday after posting bond on charges unrelated to his daughter's disappearance.

Baker was arrested on charges of assault with a deadly weapon, failure to return rental property, writing worthless checks and other charges.

Investigators are also testing DNA from a mattress found at a Caldwell County landfill to see if it belongs to Zahra. 

The Associated Press contributed to this report