As thousands of girls and young women prepare to start the new school year in France, activists are sounding the alarm over those who are missing - teenagers sent abroad over the holidays and forced into marriage.
Most victims are of Asian, African or Middle Eastern descent and belong to France's Muslim community, the largest in Europe.
While countries such as Britain have set up special units that track down victims at home and overseas, activists say France is only now waking up to the problem.
"For a long time this used to be considered a cultural thing," said Fatima Lalem, who is in charge of gender equality at Paris City Hall.
"Something that happens, but that people don't look at too closely." Over the past year, France has begun to tackle the problem more aggressively. Last November, Paris City Hall published a guide advising officials on detecting forced marriages.
But former victims and activists, many of them second- or third-generation immigrants working in France's multicultural suburbs, said such moves were unlikely to help women married off abroad, or scared into silence.
Zeliha Alkis, who works for Elele, a non-profit organisation that mainly helps women of Turkish origin, cites the example of a young woman of Turkish descent who was married to a Turkish man at a Paris town hall this summer. On her wedding night, she was locked in a room, and when she screamed and protested, her grandmother tied her up so the marriage could be consummated.
In many other cases, the women are married in the family's country of origin. Reasons include the family wanting to ensure the woman marries a candidate deemed suitable, settling a debt and procuring a visa for the groom. Unlike arranged marriage, which can be consensual, these weddings are performed against the women's will.
"Early June to late this month is our busiest period, after the wedding was celebrated over there, and then the young woman calls us and says, what do I do now, I don't want that husband," said Ms Alkis, who has received death threats from angry families.
No one knows exactly how many French women are forced into such unions. A report on women's rights by France's high council for integration in 2003 put the number of girls and women at risk of being forced into marriage at 70,000, based on research by grassroots organisations.
Christine Jamaa, head of non-profit organisation Voix de Femmes, and her team help more than 200 women a year flee forced marriages or escape before the wedding.
Since more than half of them are under the age of 20 and at school or college, Jamaa is asking the government to set up an early warning system for those who disappear over the holidays.
"There are those who don't come back from the summer holidays and sometimes the schools only react in October, even in February," said Ms Jamaa at her office north of Paris.
France has at times steered an awkward course between trying to respect its ethnic minorities and defending women's rights; last year, a French court annulled the marriage of a Muslim woman on the grounds that she lied about being a virgin.
Similarly, some see forced marriage as a religious issue, even though Islam bans it and imams helping the women have been threatened.
In the families' countries of origin, forced marriage tends to be illegal and less widespread than in migrant communities.