Jahi McMath left the hospital in a private ambulance shortly before 8 p.m. Sunday, Christopher Dolan told The Associated Press.
She was taken by a critical care team while attached to a ventilator but without a feeding tube, Dolan said. Her destination was not immediately disclosed.
"It was a very tense situation," said Dolan. "Everybody played by the rules."
David Durand, the hospital's Chief of Pediatrics, said the girl was released to the coroner. The coroner then released her into the custody of her mother, Nailah Winkfield, as per court order, Durand said in an email.
On Friday Alameda County Superior Court Judge Evelio Grillo said Jahi could be transferred under an agreement with Children's Hospital and the girl's mother will be held accountable for developments that could include Jahi going into cardiac arrest.
The Alameda County coroner's office issued a death certificate for the girl Friday but said the document is incomplete because no cause of death has been determined pending an autopsy.
"They may have issued one but we don't have it. We don't think she's dead," Dolan said. "We got all the necessary legal paperwork in order to get Jahi out of there."
A court injunction prohibiting Children's Hospital from removing the ventilator that has kept Jahi's heart pumping since her Dec. 9 surgery expires at 5 p.m. Tuesday.
Dolan wouldn't specify where the girl was taken but he said "they are going to care for her, respect her and love her. And they're going to call her Jahi, not 'the body.'"
After spending weeks in a very public and tense fight with the hospital, Jahi's family does not plan to disclose any more about their plans for her continued care until she is resettled, her uncle, Omari Sealey, told reporters on Friday.
The hospital has argued since before Christmas that Jahi's brain death means she is legally dead and she should be disconnected from the ventilator. It also has refused to fit her with a feeding tube or a breathing tube that would help stabilize her during a move, saying it was unethical to perform medical procedures on a dead person.
Hospital spokesman Sam Singer said officials were not informed where the girl was being taken.
"We hope that the family finds peace in this very, very tragic story," he said.
Winkfield, refusing to believe her daughter is dead as long as her heart is beating, has gone to court to stop the machine from being disconnected. She has wanted to transfer Jahi to another facility and hoped to force Children's Hospital either to insert the tubes or to allow an outside doctor to do the procedures.
Grillo on Friday rejected the family's move to have the hospital insert the tubes, noting the girl could be moved with the ventilator and intravenous fluid lines she has now. He also refused to compel the hospital to permit an outside doctor perform the procedures on its premises.
Dolan said Friday the family has located an unaffiliated physician to put in the tubes and that an outpatient clinic in New York that treats people with traumatic brain injures has expressed willingness to care for Jahi.
Jahi went into cardiac arrest while recovering from surgery to remove her tonsils, adenoids and uvula along with bony structures from her nose and throat and palate tissue. Three doctors have declared the girl brain dead based on exams and tests showing no blood flow or electrical activity in either her cerebrum or the brain stem that controls breathing.
Multiple outside doctors and bioethicists observing the case have confirmed that a patient in that condition meets the legal criteria for death and has no chance of recovering.
The judge earlier this week ordered Children's Hospital to keep Jahi on the ventilator until Jan. 7 at 5 p.m. He said Friday that he would dissolve the injunction as soon as Winkfield assumes custody of her daughter's body.
Hospital spokesman Sam Singer said that if the girl is not transferred by the deadline, her family would have to seek an extension or the ventilator would be removed.