Investigators in North Carolina are searching a landfill Wednesday for a "piece of evidence" in the case of missing 10-year-old Zahra Baker, whom authorities have been struggling to find for more than a week.

The Hickory Police Department said Wednesday that a team of local, state and federal investigators are scouring a landfill in Lenoir, N.C. -- approximately 18 miles from Zahra's home in Hickory -- for evidence in the girl's disappearance.

Hickory Police Chief Tom Adkins did not describe the evidence in a press conference with reporters, and said he did not expect to the find the girl's body in the Foothills Environmental Landfill. 

"We hope that if we find this evidence that it will provide a good, solid timeline that will assist us in working this case," Adkins said. 

Zahra was reported missing on Oct. 9 and police accused Elisa Baker, the girl's stepmother, of writing a fake ransom note.

Zahra, a bone cancer survivor, had a prosthetic leg and hearing aids that were found at the home after she was reported missing.

Police on Tuesday released the recording of a 911 call that Zahra's father, Adam Baker, made to authorities -- claiming the child had been mistaken for another girl in a ransom ploy.

Baker told a Hickory Police Department dispatcher that a ransom note was found indicating that someone kidnapped his boss' daughter after someone set a fire in his backyard.

"The police were out here last night and found a ransom note for my boss' daughter. It appears they took my daughter instead of my boss' daughter," Baker said in the 911 call. He says in the note that the kidnappers were going to come for his boss' son next.

Baker also told the dispatcher that he didn't realize his daughter was missing until afterwards because, as he puts it, she rarely comes out of her room.

"My daughter, I think, is coming into puberty... so we only see her when she comes out and wants something."

Investigators said Tuesday they want medical records from Zahra's native Australia, including details on the prosthesis she's had since losing a leg to bone cancer.

Hickory Deputy Chief Maj. Clyde Deal said detectives need to know the model, serial number, and composition of the artificial leg from the Australian medical facility that fitted it for Zahra.

Authorities say she was last seen in public on Sept. 25. 

A judge increased the bond for Elisa Baker on Wednesday to $65,000 after prosecutors convinced him she was a flight risk. She was charged with felony obstruction of justice after police said she confessed to leaving the handwritten note on the windshield of one of the family's vehicles. 

During Baker's court appearance Wednesday, her attorney asked District Judge Robert Mullinax Jr. to reduce her bond on the charge to $10,000. Bail had been $45,000. 

Prosecutors asked for a $100,000 bail, saying Baker had failed to appear in court before and had been talking to a man from England on the Internet before she was jailed.

FoxNews.com's Cristina Corbin and the Associated Press contributed to this report