ROME—Thousands of visitors file through the palatial museum rooms of the Doge’s Palace on St. Mark’s Square in Venice every single day. In fact, most of the exhibits like “Treasures of the Mughals and Maharajas” showcasing 270 precious gems and sparkling jewelry from the private collection of Hamad bin Abdullah Al Thani of the royal family of Qatar, open as early as 8:30 in the morning to help ease the flow and make the visit more enjoyable.

By 10:00, the tour groups are in place, adding to the chaos of the steady flow of people in and out of the exhibit rooms. And so it was on Wednesday when two people dressed in winter coats approached an jewel case in the “Scrutiny Room” with several dazzling brooches and earrings worth as much as a million dollars.

They stood for a moment pretending to admire the collection until the room partially emptied before they skillfully opened the case and managed to grab several precious pieces before the alarm even went off. By the time the security guards arrived, a few seconds after the alarm bells sounded, the thieves had already mixed into the crowd, likely leaving the museum and blending easily into the masses in St. Mark’s Square.

The exhibit, which was described in promotional material by Doge Palace curators as replete with “dazzling gems, precious stones and jewels brimming with centuries of history and legend” is of uncommon value for a jewelry exhibit in Venice. Previously it drew crowds at the Grand Palais in Paris, and some of the treasures in the collection have been shown in London as well.

The exhibit was set to close its three-month run later in the day, making it the last chance the thieves had to make their move. Venice Chief of Police Vito Gagliardi believes they had visited the exhibit perhaps more than once before their daring theft, likely to determine the type of security and to gauge both the size of the crowds and possibly even what they tended to wear at any given time of the day to make it easier to escape.

Surveillance video, which has not been released to the public pending the investigation, apparently shows the two thieves move toward the case. (Their gender has not yet been identified publicly by the police.) One person made a series of agile movements, slipping the jewels in an inside jacket pocket while the other stood in the way of the surveillance camera, according to Vice Police Commissioner Marco Odorisio in a press conference on Wednesday afternoon.”The theft is a classic mosaic: we must start from the details and then step back and a look at the bigger picture to see who committed the theft,” he said. “It is premature to talk about Italian or foreign authors.”

A spate of jewel thefts has rocked Europe in recent years, from the theft of $9 million worth of Kim Kardashian’s diamonds from her Paris hotel to a hotel safe heist at Cannes. In 2015, thieves in Venice let off smoke bombs and tried to steal a handful of diamonds from a jewelry shop in St. Mark’s Square but were foiled when police, thinking it was a terror attack, responded in force.

It is rare that jewelry is recovered from such robberies. Investigators working on the Doge Palace heist believe that the pieces, if kept intact, would be difficult to sell on the black market because they could be easily recognized. More likely they will be dismantled and the precious gems and diamonds sold individually, making them much harder to trace. Experts from Rome’s elite cultural police have been called to lead the investigation.

Gagliardi believes the thieves “were experts in surveillance and alarm systems” and may have even been working with others in the crowd. He dismissed any theory that involved a faulty system at the Doge Palace. “Technological knowledge from the highly sophisticated thieves allowed them to delay the alarm and open the case containing the jewels without breaking it,” he said. “It’s important to understand what didn’t work. They opened the case as if it were a tin can and got out before the alarm even sounded. We need to understand how that happened.”