Kristen Lee Dutton, 9, was walking the dog by herself Saturday when the attack took place, McCormick County Coroner Faye Puckett said.
"We're not sure what happened to make the dog attack," Puckett said. Family members said the family pet -- which they had had three weeks -- had shown no signs of aggression previously.
The dog, a 98-pound Japanese Akita that was a gift from the child's grandfather, was secured at the family home over the weekend, the coroner said.
The state Department of Health and Environmental Control said Monday a test for rabies was negative.
The coroner said the girl was walking the dog alone near Modoc Shores on Saturday when the attack is believed to have happened. She was bitten in the neck, and was found by a family member and later pronounced dead at Medical College of Georgia Hospital.
Sandra Friar, a spokeswoman for Edgefield County schools confirmed Kristen was a fourth-grader at the school and said counselors were made available Monday.
A funeral is scheduled Wednesday at Posey Funeral Chapel, North Augusta.