The whole raid took just seven minutes, say officials / AFP

The Louvre was closed for a second day Monday as police hunted for thieves who broke in and stole priceless jewels in a spectacular daylight robbery.

Officials said a team of 60 investigators was working on the theory that an organised crime group was behind the theft Sunday of nine pieces of jewellery, one of which -- a crown covered in more than 1,000 diamonds -- they dropped as they fled.

The thieves arrived at around 9:30 am (0730 GMT), shortly after the museum opened at 9:00 am, and completed the robbery in just seven minutes, sources and officials said.

They parked a truck with an extendable ladder like those used by movers below the museum's Apollo Gallery, home to an imperial jewel collection, clambering up and using cutting equipment to get in through a window and open the display cases.

The world-famous museum, whose extensive collections include the Mona Lisa, said it was closing for a second day.

"Following yesterday's robbery at the Louvre, the museum regrets to inform you that it will remain closed to the public today," it said on its website.

At the museum, US tourist Jesslyn Ehlers, 38, and her husband were busy rebooking their tickets. 

"We're just kind of disappointed. We've been planning this for a very long time," she said.

Shortly before the announcement, queues of impatient visitors snaked their way across the museum's pyramid courtyard and under the tall arches of the main entrance gallery.

Carol Fuchs, an elderly tourist from the United States, had been standing in line for more than three-quarters of an hour.

"The audacity, coming through a window," she told AFP after the disappearance of the jewels.

"Will they ever be found? I doubt it. I think it's long gone," she said.

- Diamonds, sapphires missing -

The masked thieves dropped and damaged the crown of the Empress Eugenie, the wife of Napoleon III, as they made their escape. It is covered in 1,354 diamonds and 56 emeralds, according to the museum's website.

But eight priceless items of jewellery remain missing, according to the culture ministry.

The list they released included an emerald-and-diamond necklace that Napoleon gave his wife Empress Marie-Louise.

Also stolen was a diadem that once belonged to the Empress Eugenie, which is dotted with nearly 2,000 diamonds, and a necklace that once belonged to Marie-Amelie, the last queen of France. It is adorned with eight sapphires and 631 diamonds, according to the Louvre's website.

The loot would be impossible to sell on in its current state, said Alexandre Giquello, president of the leading auctioneer house Drouot.

The heist reignited a row over a lack of security in France's museums, with Justice Minister Gerald Darmanin admitting Monday to security flaws in protecting the Louvre.

"What is certain is that we have failed, since people were able to park a furniture hoist in the middle of Paris, get people up it in several minutes to grab priceless jewels, giving France a terrible image," he told France Inter radio.

- 'Foreigners'? -

After several other robberies from French museums in recent months, Interior Minister Laurent Nunez had acknowledged Sunday that securing them was a "major weak spot".

The whole raid took just seven minutes and is thought to have been carried out by an experienced team, possibly "foreigners", Nunez said.

The intervention of museum staff forced the thieves to flee, leaving behind some of the equipment used in the raid, the culture ministry said.

It was the first theft from the Louvre since 1998, when a painting by Camille Corot was stolen and never seen again.

Sunday's raid relaunched a debate over what critics says is poor security at the nation's museums, far less secure than banks and increasingly targeted by thieves.

Last month, criminals broke into Paris's Natural History Museum, making off with gold samples worth $700,000.

The same month, thieves stole two dishes and a vase from a museum in the central city of Limoges, the losses estimated at $7.6 million.

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