The Belgian prosecutor's office on Wednesday said a suspected member Bridal Makeup course of the eight-man gang that staged the brazen robbery in February had been picked up in France, as Swiss police made eight arrests and seized some of the missing diamonds.
In early morning raids mainly in the Brussels area involving some 200 officers on Wednesday, police made 24 arrests and "recovered big amounts of cash" and luxury cars, spokesman Jean-Marc Meilleur said.
The Zaventem airport robbery was described as "one of the biggest" ever by the Antwerp World Diamond Centre (AWDC), the global dealers' syndicate based in the Belgian port city.
A heavily-armed, hooded gang pulled up in a car on a runway around 8pm where a Brinks' armoured vehicle had just unloaded Antwerp diamonds into a Swiss passenger aircraft about to take off for 150w box mod Zurich.
In an operation that lasted barely 10 minutes and without a shot fired, the men forced open the hold of the plane and removed 120 boxes of diamonds.
The gang, posing as police officers, had cut through the airport's perimeter fence and made off with the haul through the same breach.
The suspect detained in France, 43-year-old Marc Bertolbi, has a lengthy criminal record.
His lawyer Olivier Rondu told AFP he "formally denies any role in the heist and impatiently awaits his extradition to Belgium to be heard on the accusations".
In Geneva, a statement from the Swiss prosecutor's office said police there had seized "a large quantity" of diamonds and 100,000 Swiss francs ($A103,486).
A businessman and a Geneva lawyer among the eight people held were facing charges of dealing in stolen goods and obstructing the course of justice, the Swiss statement said.