A woman who told police she had been subjected to a racist attack in which three men set her alight and scrawled KKK on her car was lying, according to US investigators.
"The wounds were self-inflicted," said Kyle Hanrahan, a spokesman for the FBI's Louisiana bureau.
Sharmeka Moffitt, 20, was seriously burned in the fire and remains in a critical condition.
She called police from a park in the town of Winnsboro on Sunday night and told them three men in white hoodies had doused her with a flammable liquid and ignited it.
The letters KKK, for the white supremacist organisation Ku Klux Klan, and a racial slur were scrawled on her car in what appeared to be toothpaste.
According to local media, investigators decided the burns were self-inflicted after finding Ms Moffitt's fingerprints on a cigarette lighter and lighter fluid.
Louisiana's KATC News reported her family had issued a statement saying: "Our family is devastated to learn the circumstances surrounding our daughter's injuries.
"While this was not the resolution we had expected, it is a resolution, and we appreciate the thorough investigation by the local and state police as well as federal agencies.
"We are sincerely sorry for any problems this may have caused and wish to express our appreciation for the outpouring of love, prayers and support we have received from friends, acquaintances, church organisations and government officials."
The FBI was called in to assist local authorities because the apparent attack was initially considered a possible hate crime.