Thirty-one people have been detained in a three-nation investigation after robbers pulled of a spectacular $50 million diamond heist at Brussels Airport some three months ago.

According to The Associated Press, a Frenchman who is believed to have been one of the actual robbers was detained in France, while six people were detained in Switzerland and 24 more in Belgium. Police also say they have proof that diamonds found in Switzerland were part of the stolen cache.

The sweep, held early Wednesday morning, involved 250 police officers and 40 house searches. 

Read more about the original heist here.