No charges have been filed and police said they have not yet interviewed all the girls, ages 12-14, who are students at Clarksville Middle School in Indiana. The girls' identities were not released because they are juveniles.
The victim, who was treated for cuts and bruises at a hospital, was the daughter of a police officer, said Police Chief Dwight Ingle.
Ingle told CBS' The Early Show that the girls were using rocks as weapons.
"You can actually hear the rocks thumping on the skull of the victim," he said.
Police said the girls lured the victim to a parking lot near a warehouse in the town just north of Louisville, Ky., on April 12 and beat her up. The violence was videotaped and later posted on the video-sharing Web site PhotoBucket, Ingle said. It has since been removed.
The video begins with one girl arguing with the victim and escalates into a fight during which the 12-year-old is repeatedly hit in the head as other girls watch and laugh, police said.
Detective Darrell Rayborn said Thursday police believed the plot was inspired by a similar scheme in which a group of teenage girls in central Florida posted the videotaped beating of a 16-year-old victim online. Parts of that video have been widely seen on TV and YouTube.
Clarksville school Superintendent Stephen G. Fisher said he did not anticipate disciplinary action against the students because the fight did not occur on school grounds.