Last week, investigators discovered a bone that police say "may be related to" the case. Police have sent the bone to a medical examiner's office to determine its relation to the case.
Police have also searched a landfill, the Bakers' home, areas where Elisa Baker formerly lived, and drained two ponds in the hunt for Zahra's remains. They pulled a mattress from the landfill and are testing it for DNA evidence, police have said.
Next Tuesday, Nov. 16, would have been Zahra's 11th birthday.
Jailhouse letters, apparently written by Elisa Baker, claim police know exactly where the girl's body is located.
The letters maintain neither Elisa Baker nor her husband killed Zahra, but that the father did something "horrifying" after the girl was dead.
The letters, obtained by ABC News, appear to shift any blame from Elisa Baker to her husband Adam Baker.
"We really didn't kill her, but what he did after the fact is kinda horrifying," Elisa Baker wrote to crime memorabilia dealer Eric Gein from jail. "[It] makes me scared of him. So I probably am gonna go ahead and file [for divorce]. I have lost my whole life anyway."
Gein, who runs the website SerialKillersInk.net, told ABC News he contacted Elisa Baker by letter weeks ago under an assumed name. The letters he received in return describe strained life in the Baker home. She allegedly signed one letter, "Dark Love Always, Elisa."
Further down the page between doodles of candles and a spider she writes, "Goth's Rule [sic]" and "Vamps Rule!" The comments are similar to those made on a MySpace page believed to belong to Elisa Baker.
"The cops know where she is and what he has done," she wrote, apparently referring to her husband.
"[Adam Baker] knows what happened to Zahra, and yet I'm the one in here at least for now," she writes.