Belgium has handed over to France Hamza Attou, who helped key Paris attacks suspect Salah Abdeslam flee to Brussels, the federal prosecutor's office said on Thursday.
"Hamza A. has been surrendered to the French authorities yesterday," a statement said, using the restricted formulation of his name.
"No further information will be given concerning the exact time or the circumstances of his transfer."
Attou, a Belgian national who has been previously identified by his lawyer, drove Abdeslam back to Brussels shortly after the Islamic State-claimed attacks in Paris left 130 dead and hundreds more wounded.
Abdeslam, the last surviving member of the Paris IS cell, was extradited to France in April.
Earlier this month, the Belgian authorities approved a French extradition request for Mohamed Abrini, the "man in the hat" seen on CCTV footage with two bombers who blew themselves up at Brussels airport in March.
The airport blast and another attack on the Brussels metro killed 32 people.
Abrini has not yet been handed over pending further investigation into the Brussels attacks.
