Italian authorities put the overall value of the collection at several million euros
Thieves have stolen several items of Indian maharajahs' treasures owned by a member of the Qatari royal family.
The theft followed a heist at the Doge's Palace in Venice, police said.
Italian authorities put the overall value of the collection of Treasures of the Mughals and the Maharajahs on display at several million euros.
Police believe two thieves got away with earrings and a brooch on Wednesday - the final day of a four-month exhibition that featured some 270 items showcasing five centuries of Indian craftsmanship.
Detectives said one kept watch while the other opened the display case and grabbed the jewelled golden brooch and earrings.
The thieves, whom police said appeared to have been part of a larger gang, seemed to have been able to delay the museum's alarm system which only sounded when they were already escaping.
They then disappeared among the crowds to make their escape.
The alarm was raised several hours later at the palace, known as the Palazzo Ducale, in central Venice in St Mark's Square.
Chief police commissioner Vito Gagliardi said. "We are clearly dealing here with two skilled professionals who managed to pull off their feat despite all the display rooms being fitted with technologically highly sophisticated (alarm) systems."
A spokesman for the collection, John Maxse, said it was in contact with Italian authorities and Venice's Foundation of Civic Museums, which runs the Doge's Palace.
Venice police said the items are so unique they will be nearly impossible to sell on the market.
The collection was assembled by Sheikh Hamad bin Abdullah Al Thani and now belongs to Qatar's ruling family.