French police detained football internationals Franck Ribery and Karim Benzema for questioning on Tuesday as part of a probe into an alleged under-age prostitution ring, legal sources told AFP.
Police have until 9:00 am (0700 GMT) on Thursday to decide whether to release the pair or bring them in front of a judge to face a charge of paying for sex with a minor that could see them jailed for three years.
The footballers were held at the request of an investigating magistrate probing claims that a Champs Elysees nightclub provided clients access to minors working as call girls, the source close to the inquiry said.
They were detained at the headquarters of France's BRP vice squad on the Ile de la Cite in central Paris. Officers can hold them for 48 hours before deciding whether to refer them to a judge to face possible charges.
One of the young women who is alleged to have met clients at the Zaman Cafe testified to investigators earlier in the year that she had had relations with the two players while she was still under 18.
If they are charged and convicted of soliciting and paying for sex with a minor, the pair face three years in jail and a fine of 45,000 euros (58,000 dollars), but only if prosecutors prove they knew she was underage.
A grim-faced Ribery arrived at the vice squad building with an assistant but refused to answer questions from reporters. It was not clear when Benzema arrived, but judicial sources said both were formally detained at 9.00 am.
Ribery's lawyer, Sophie Bottai, told reporters in front of the police station that her client had had no idea the young woman was under 18 when he had paid for sex with her in 2009.
Benzema's counsel was not immediately available for comment.
Boulogne-born 27-year-old midfielder Ribery plays for Bayern Munich in Germany and was a member of France's ill-fated squad which went out in the first round at this month's 2010 World Cup in South Africa.
Real Madrid striker Benzema, 22, missed out on this year's French team despite playing in much of the World Cup qualifying campaign.
The young woman, Zahia Dehar, is now 18 years and four months old. She has been questioned by police and gave a tell-all interview to the news and gossip weekly Paris Match after the scandal erupted.
She described selling sexual encounters to Ribery in 2009 and to Benzema in 2008, while she was underage, and with a third French player, 30-year-old Panathinaikos winger Sidney Govou, in March, when she was an adult.
Dehar has said the players did not know she was a minor. In France the general age of consent is 15 years, but in the case of prostitution a young person remains legally a minor until he or she reaches 18.
Adult prostitution is in itself legal in France, but pimping, solicitation and running organised vice networks are outlawed.
The footballers became caught up in the investigation after detectives probing allegations of a vice ring bugged the Zaman Cafe, an expensive nightspot just off Paris's most glamorous street, the Champs Elysees.
Four people - including the owner of the club, a waiter who worked there and a man suspected of pimping call girls to celebrities and sportsmen - have been placed under formal judicial investigation and could face trial.