BRUSSELS, Belgium - Unlike the thieves in Ocean's Eleven, it appears that those behind the clockwork-precision, $50 million diamond heist at Brussels Airport may not get a Hollywood ending.

After three months of virtual silence, authorities struck this week, detaining at least 31 people in a three-nation sweep and recovering so many diamonds from the loot Antwerp traders lost that they are still figuring out the exact value.

Officials said that among the people held in Belgium, France, and Switzerland were some with violent criminal pasts; the one person held in France is believed to have been one of the airport robbers. The evidence seized includes large sums of cash, precious stones, and luxury cars.

The arrests were "a total surprise for us," said Caroline De Wolf of the Antwerp World Diamond Center, whose traders lost millions in the Feb. 18 heist. "But we were delighted when we heard."

Six to eight people were detained in Geneva, and 24 in and around Brussels. It was unclear exactly what roles each suspect may have played.

Some 250 police officers were involved in the dawn raid in the Belgian capital, and many of the two dozen suspects were being interrogated late Wednesday. It could take at least another day before it is clear how many will be arrested, said Anja Bijnens of the prosecutor's office.

The value of the diamonds recovered was still being estimated. It was unclear how many diamonds are still missing.

The Feb. 18 heist was stunning and brazen.

The stones from the global diamond center of Antwerp had been loaded on a plane bound for Zurich when robbers, in dark police clothing and hoods, drove through a hole they had cut in the airport fence in two black cars with blue police lights flashing.

They drove onto the tarmac, approached the plane, waved machine guns, off-loaded the diamonds, then left in an operation that barely took five minutes.