Police in France believe priceless antique jewelry stolen from the Louvre Museum in Paris on Sunday could be broken into constituent jewels, re-cut and sold.

The building remained closed on Monday as the investigation continued. Prosecutors said four thieves used battery-powered disccutters or mini chain saws to enter the world's most-visited museum during the daylight raid, using a mechanized cherry-picker to gain access and two scooters to escape.

They made off with nine extremely valuable items from France's "royal jewels", including diadems, necklaces, earrings and brooches made in the 19th century for members of the royal family and imperial rulers.

One of the items, a crown made for Napoleon III's wife, the Empress Eugenie, was apparently dropped as the thieves escaped. The ornate gold piece featuring 1,354 diamonds and 56 emeralds was damaged during the theft, the French TV station TF1 and the newspaper Le Parisien reported.

The minister of culture, Rachida Dati, told TF1 that investigators have video of the thieves entering the ornate, gold-gilded Galerie d'Apollon, on the first floor of the museum, "calmly" before smashing display cases.

They did not use violence and appeared "very professional" and "experienced", she said.

The interior minister, Laurent Nunez, told France Inter radio that they moved "very, very fast" and that the heist was over in less than seven minutes, between about 9:30 am and about 9:40 am.

The stolen items were "priceless" and "of immeasurable heritage value", Nunez said.

The thieves told security guards to evacuate the area while they opened two glass display cases, police said. The Ministry of Culture confirmed that museum workers correctly followed procedure and did not attempt to tackle the thieves.

Arthur Brand, an art recovery expert, told CNN that the theft amounts to a "national disaster" for France.

"These are the crown jewels from Napoleon, his wife and his successors. So these are the natural pride of France. It's a great loss."

Jordan Bardella, leader of France's far-right National Rally party, put the blame at the foot of the government, writing on X: "The Louvre is a global symbol of our culture. This robbery, which allowed thieves to steal jewels from the French crown, is an unbearable humiliation for our country. How far will the decay of the state go?"

Nathalie Goulet, a member of the French Senate's finance committee, told the BBC that "we are all disappointed and angry".

"(It is) difficult to understand how it happened so easily," she said.

Justice Minister Gerald Darmanin agreed, telling France Inter, "People were able to park a furniture hoist in the middle of Paris, get people up it in several minutes to grab priceless jewels and give France a terrible image."