A French woman who alleged she had been the subject of an anti-Semitic attack invented the story, police sources say.
The reported assault follows a rise in anti-Semitic attacks
The alleged admission came shortly after the she was taken into custody - four days after the alleged assault on a train in the suburbs of Paris.
The 23-year-old woman said six men cut her clothes and drew swastikas on her body, assuming that she was Jewish.
The woman has been detained for falsely reporting a crime, state prosecutor Xavier Salvat told AFP news agency.
She could face up to six months in prison and a 7,500-euro ($9,200) fine if convicted.
The case sparked widespread condemnation amid concern that racist and anti-Semitic attacks are on the rise in France.
The woman initially described the men as being of North African appearance, and said they tipped her 13-month-old baby from her pram.
She said about 20 people could have seen the attack but no-one has come forward.
Investigators studied footage from surveillance cameras at the train station where the six alleged attackers were supposed to have got out but found nothing.
Now unnamed police sources say she has admitted drawing the swastikas with the help of her boyfriend who is also in custody.
French media report that the young woman has filed several complaints in the past about being the victim of violence.
The reported brutality of the attack on the woman, its anti-Semitic character and the fact that no-one came to her help provoked outrage.
It also added to growing concern over racist and anti-Semitic attacks.
President Jacques Chirac, who condemned the alleged assault as "shameful", said he would deny clemency to any prisoner serving time for a racist crime.
Government spokesman Jean-Francois Cope told RTL radio a rising trend of anti-Semitic attacks was "a genuine evil" in France, even if the woman's case might not be real.