BRUSSELS – Unlike the brilliant 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 on the matter, 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 on Tuesday and Wednesday are some with violent criminal pasts; the one person held in France is believed to have been one of the robbers at the airport. The evidence seized includes large sums of cash, precious stones and luxury cars.

“It was 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.

Some 250 policemen were involved in the dawn raid in the Belgian capital. The theft ranks among the biggest diamond heists of recent times, and many liken it to the plot of the 2001 Vegas heist movie, “Ocean’s Eleven,” which stars George Clooney, Brad Pitt and Matt Damon, for its clean execution.