Police questioned 31 people in three European countries on Tuesday and Wednesday in relation to the major diamond heist that took place on the tarmac of Brussels International Airport in February, a spokeswoman for the Brussels prosecutor’s office confirmed.

This story first appeared in the May 9, 2013 issue of WWD.  Subscribe Today.

Police detained 24 people in Belgium, six in Switzerland and one in France. Those questioned in Belgium ranged from 30 to 50 years of age, and a number were already familiar to police. Among the 24 detained, at least 10 were “very known” criminals, said the spokeswoman.

Searches, which continued Wednesday, uncovered diamonds in Switzerland linked to the holdup. Large sums of money and luxury vehicles were also seized in Belgium, the spokeswoman confirmed.

The spectacular hit-and-run operation on Feb. 18 involved a gang of eight heavily armed men disguised as policemen, who made off with a haul of rough and polished diamonds estimated to be worth $50 million. They were stolen from a plane that was en route to Zurich from Antwerp.

The raid, which is said to have lasted only three minutes and occurred shortly before takeoff, was among the biggest diamond heists ever.