A French judge decided on Tuesday to keep Swiss Islamic scholar Tariq Ramadan in custody pending a possible trial for allegations of rape, a source with the prosecutor's office said.
Ramadan, who denies the allegations, was notified on Friday that he would be the target of a full investigation and had been in detention since.
After a debate between his lawyers, prosecutors and magistrates, judges decided not to release him, taking the inquiry a step further.
Under French law, investigating magistrates can still decide not to hold a trial, depending on the evidence. Temporary custody is usually reserved for cases where the accused might be a flight risk.