The initial police examination/interrogation has ended ("garde à vue"), and he's now been brought before a judge who will decide if he should be freed or kept in an actual jail (which a police station isn't).
Until the judge makes that decision he's still very much detained by the police (albeit not interrogated).
In the USA police can generally hold someone for 24-48hours before actual charges are filed (it takes a minute to generate an indictment), allowing them to investigate and interrogate.
Then, if an indictment is filed a judge makes a decision on pre-trial confinement until trial. In France there is a general four month limit on pre-trial confinement before it has to be heavily justified.
We have "garde à vue" and "détention provisoire":
- "Garde a vue" is similar to being in police custody and it's limited to 24-48 hours normally, but there is longer duration for specific crime, the maximum being 6 days for terrorism investigations [0].
- Then, a judge can decide that the defendant should stay in "détention provisoire" before a trial. It doesn't have a duration limit but should be motivated and can be re-examined multiple time [1].
0: https://fr.wikipedia.org/wiki/Garde_%C3%A0_vue_en_droit_fran... 1: https://fr.wikipedia.org/wiki/D%C3%A9tention_provisoire_en_F...