The search lasted until about 3 a.m. Wednesday, according to CNN affiliate WSOC, and authorities plan to continue searching the same area after taking a break for a few hours.
Flanked by two attorneys, Elisa Baker, Zahra's stepmother, wore a bright pink jumpsuit and was handcuffed and chained at her wrist and ankles at her court appearance Wednesday. She was informed of the felony charge against her, which carries a penalty of more than two years in prison upon conviction. Asked if she understood, she affirmed in a low voice.
The bond on the obstruction of justice charge is $40,000, in addition to the bond of more than $30,000 she faces on charges unrelated to Zahra's disappearance. Her attorney, Scott Reilly, said he would be filing a motion to get the bond reduced, calling it "excessive." She is next scheduled to have a probable cause hearing on November 3.
Reilly told reporters $10,000 is usually a maximum bond for such a charge. He said his client is scared, emotional, upset and worried about her family. Asked what she has said about Zahra, he said he was not at liberty to discuss the girl.
The case is an emotional one for investigators and a high priority, Catawba County District Attorney Jay Gaither Jr., told the assembled reporters, who came from as far away as Australia.
"The facts are disturbing as we know them at this point," he said. "... We want the best but we fear the worst."
Elisa Baker was charged with obstruction of justice Tuesday after police said she admitted writing a ransom note found at the family's Hickory, North Carolina, home.
During the search overnight, Zahra's emotional father, Adam Baker, was on the scene.
"He seems concerned," Burke County Sheriff John T. McDevitt said. "But I don't know how sincere his concern is."
Zahra was reported missing about 2 p.m. Saturday. Police have said her father and stepmother reported she was last seen sleeping in her bed about 12 hours earlier, at 2:30 a.m.
But Hickory Police Chief Tom Adkins said Tuesday authorities have been unable to find anyone outside Zahra's immediate family who has reported seeing her in the past month, and investigators are not sure how long she has actually been missing. He told reporters an Amber Alert issued after the girl was reported missing was being canceled, and the investigation has shifted from a possible abduction into a homicide probe.
Investigators were searching where Adam Baker worked north of Hickory, said Nancy Webb, who lives next door to the site, on Tuesday.
Adam Baker would help his employer bring piles of wood and brush to the lot, where it was dumped into a wood chipper and turned into mulch, Webb said.
"They've got a lot of lights out back of the house. It looks like they are doing a search around a brush pile, and that's all that I can see from the house here," Webb told HLN's "Nancy Grace."
Elisa Baker admitted writing the note Monday night during an interview at the jail where she is being held on charges of writing worthless checks, Adkins said. She then requested a lawyer, he said. Police obtained an arrest warrant for her on the obstruction of justice charge.
A search warrant application filed in the case said it began with a call about a burning mulch pile at the family's home about 5:30 a.m. Saturday. Firefighters found a Chevrolet Tahoe with its passenger door open and a power company envelope with handwriting on it on the front windshield, the search warrant said.
Firefighters notified police, who approached the SUV and smelled gasoline coming from inside. The note written on the envelope was addressed to a "Mr. Coffey," identified in the search warrant as Adam Baker's boss, Mark David Coffey.
"Mr. Coffey, you like being in control now who is in control," the note said, according to the search warrant. "We have your daughter and your pot smoking red head son is next unless you do what is asked 1,000,000 unmarked will be in touch soon." In the bottom right, the note said, "no cops," according to the warrant.
Coffey and his only daughter were at the residence at the time of the fire, the warrant said. CNN affiliate News 14 Carolina reported Coffey owns the home.
Adam Baker called police about 2 p.m., saying someone had poured gas in his car and left a note saying they had his boss' daughter, according to the search warrant. Baker told police he believed the person who left the note had kidnapped Zahra.
The Bakers consented to a search of their home, the warrant said. A cadaver dog indicated the possible presence of human remains in or on the Chevrolet Tahoe as well as a burgundy Toyota Camry on the property, it said. Authorities were testing swabs taken from the Tahoe to determine if blood was also present, according to the warrant.
Zahra -- a bone cancer survivor, according to CNN affiliate WCNC -- uses a prosthetic leg and hearing aids. The hearing aids have been found, but not the prosthesis, Adkins said.
Elisa Baker was arrested Sunday morning on four counts of writing worthless checks, said Eric Farr, a spokesman for the Catawba County district attorney's office. Farr said she faces other charges in different counties, including a felony larceny count and other bad-check charges. She was being held on $31,500 bail.
Adkins said Adam Baker faces similar charges, but police have held off serving an arrest warrant while he cooperates with investigators. And police said in a statement they are "working several leads, specifically addressing Zahra's life before she disappeared."
Brittany Bentley, who is married to Elisa Baker's nephew, told HLN that the girl "wasn't in very good living conditions, not at all for a 10-year-old."
"I remember Elisa coming out of the bedroom one day, saying her hands hurt from spanking Zahra so much," she said. "I know she spanked way too hard, what I consider beating." She said the girl was locked in her room and "I know about letting her out five minutes, just to eat and that was it."