The incident happened Wednesday evening, the Savannah Morning News reported.
County Deputy Sheriff James Beatty said his office received a report at 6:21 p.m. from the girl's grandmother, who said she looked out her window and saw the attack happen.
The grandmother said she rushed outside with other people to pull the dogs -- all pit bulls or pit bull mixes -- off the child, but it was too late.
"When we got here and spoke to EMS [Emergency Medical Services], they told us that when they got here, she was already cold. There was nothing they could do," Beatty said.
How the girl, who would have been 2 in June, got into the back yard was still unknown. Beatty said her 12-year-old brother may have brought her out to play and accidentally left her outside alone, or she may have gone out through the doggy door.
The seven dogs involved in the attack, which lived at the girl's house, were euthanized at the scene by Bryan County Animal Control. Two other dogs at the residence, which were not pit bulls and were not involved in the attack, were spared.
"All the dogs had access to the house, nine dogs in all," Sheriff Clyde Smith said. "She habitually played with dogs, all of them. But they drug her all over the yard. Something turned them on her. We don't know what."
Smith said the girl's body has been transferred to a crime lab for an autopsy.
"The investigation is continuing," Smith said.
Yosemite climber falls 30 feet, suffers major injuries
'How to Train Your Dragon 2' releases 5-minute clip