Police told The Charlotte Observer the 10-year-old Hickory girl's parents disposed of her mattress just days before reporting her missing Oct. 9.
Authorities had searched the Foothills Environmental Landfill in Lenoir County since Wednesday, looking for evidence for a timeline of Zahra's disappearance. They revealed Friday that they wanted the mattress to back up information from witnesses and possibly get DNA evidence.
Police believe Zahra is dead and are investigating the case as a homicide. The girl, who lost a leg to cancer, has not been seen alive since Sept. 25.
A state senator said he will push for an investigation of how the state handled alleged reports of child abuse against Zahra's stepmother, Elisa Baker.
"People are horrified by this and sickened by it," said Republican state Sen. Austin Allran.
His comments come after the Charlotte Observer found that at least 137 North Carolina children have died in cases in which abuse or neglect were suspected, even though state agencies had contact with their families within 12 months before they died.