A Chinese chimera in cloisonné enamel from the reign of Qianlong (1736-95). Gerard Blot / RMN-Grand palais

About 15 rare pieces of art have been stolen from the Chinese Museum of the Chateau de Fontainebleau, southeast of Paris.

They include a crown of the King of Siam, given to French Emperor Napoleon III during the king's visit to France in 1861, and a Chinese chimera in cloisonné enamel from the reign of Qianlong (1736-95) during the Qing Dynasty (1644-1911), the French Culture Ministry said in a statement.

The ministry said the break-in before dawn on Sunday at the museum in Fontainebleau Castle was over in less than seven minutes. The thefts took place in one of the most secure parts of the castle, equipped with alarms and surveillance cameras, the ministry said.

Police are investigating.

Jean-Francois Hebert, who runs Fontainebleau Castle, said, "We think they were very determined, knew exactly what they were looking for and worked in a very professional manner."

Castle spokesman Alexis de Kermel said he could not estimate the objects' value and that they are priceless and the museum's master work.

The ministry said the stolen objects were assembled by Empress Eugenie, the wife of Napoleon III, for her Chinese museum in 1863.

The crown was donated by ambassadors of Siam, now Thailand, during an official visit to France two years earlier.