Swiss police made six arrests and seized some of the missing diamonds, while a suspected member of the eight-man gang who nabbed the jewels on a Belgian airport tarmac just under three months ago was picked up in France on Tuesday, a spokesman for the Brussels prosecutor's office said.
"The probe led to a big police operation yesterday," spokesman Jean-Marc Meilleur told a news conference.
In early morning raids on involving some 200 officers, Belgian police made 24 arrests and "recovered big amounts of cash", Meilleur added.
The robbery at Brussels International Airport was at the time described as "one of the biggest" ever by the Antwerp World Diamond Centre (AWDC), the global dealers' syndicate.
The brazen heist was carried out by eight men who pulled up on a runway where a Helvetic Airways passenger aircraft was about to take off for Zurich.
The alleged robbers forced open the cargo hold to grab gems already loaded onto the plane.
A Geneva court on Friday ordered the continued detention of a lawyer and a businessman arrested in connection with the diamond heist.
It remanded the businessman in custody for another month, while it ordered that the lawyer be detained for an additional week, the Swiss news agency SDA reported.
Prosecutor Marco Rossier had asked a Geneva court to keep the two men, whose names were not given, in custody for another three months and one month respectively.