Mohamed Abrini was transferred to the French judicial authorities on Monday so that they could look into his links with the November 2015 Paris attacks.
He was to stay just 24 hours in Paris, according to French magazine l'Obs.
Two days before the November attacks, he was filmed in a filling station on the road to Paris with Salah Abdeslam, only survivor of the commando that committed the attacks.
He is also suspected to have accompanied the two suicide bombers at Brussels airport in March 2016 and to have deposited a bomb in a bag there.
He has confessed to being the "man in the hat" filmed by surveillance cameras.
Abrini was arrested in April 2016 and has since been detained in Belgium's Nivelles prison, where he is inn provisional detention.
Identified as a radical Islamist by Belgian investigators, Abrini is believed to have briefly visited Syria last year.
His younger brother Suleiman, 20, died there.
He was known to security services as belonging to the same terror cell as Abdelhamid Abaaoud, who has been identified as the principal organiser of the Paris attacks.