The alleged pattern turns on the hierarchy of a recruitment process. Investigators say the closed setting of an interview and the applicant's difficulty in refusing were used repeatedly.

Cases with large victim counts typically feature delayed reporting, whether because victims were not in a state to recognise what had happened or because they feared the effect of reporting on their careers.

France has strengthened investigative techniques and sample retention procedures for drug-facilitated offences in recent years. Wider use of tests that remain valid long after the event is cited as a reason the inquiry reached so far back.

Institutional safeguards around power relations in hiring are being discussed alongside, including keeping records of interviews and requiring a third person to be present.

Proceedings are continuing and the charges have not been determined.

Reporting on the case follows the principle of withholding victims' identities.