The invaluable jewels seized in a daring heist at the Louvre may end up dismantled and irretrievably lost, experts fear.

Following the swift, seven-minute theft on Sunday, museum officials convened an urgent meeting. The brazen raid saw an organized group make off with treasures, including an Imperial brooch adorned with 2,000 diamonds.

The stolen collection comprises eight pieces, all originating from France’s 19th-century royalty, each embedded with thousands of diamonds and other precious stones.

Among the pilfered items were a tiara, necklace, and earrings from the Queen Marie-Amelie sapphire set. Additionally, a brooch encrusted with 2,438 diamonds that belonged to Empress Eugenie, the wife of Napoleon III, was taken.

On the evening following the theft, the Louvre, renowned as the world’s most visited museum, remained closed. A critical meeting took place, including Interior Minister Laurent Nunez and Culture Minister Rachida Dati, to assess security failings.

It emerged that security personnel did not intervene with the thieves, and law enforcement was slow to respond to the triggered alarm.

Justice minister Gerald Darmanin also conceded windows and display cabinets were too easily broken into, and there were not enough CCTV cameras in the targeted Denton Wing. 

‘We failed and presented a deplorable image of France,’ he said.

The tiara, pictured, from the jewellery set of Queen Marie-Amélie and Queen Horten that was made in Paris in the 19th century, was taken

Empress Eugenie’s tiara (pictured), created by Alexandre-Gabriel Lemonnier in 1853, was stolen

Thieves also got away with an emerald necklace, pictured, from the Marie-Louise set made by master jeweller François-Régnault Nitot in 1810

Paris prosecutor Laure Beccuau said the ‘highly organised gang’ could well be working for a collector in the black market.

The gang of several ‘highly organised criminals’ arrived outside the world’s most visited museum at around 9.30am local time on Sunday while thousands of tourists enjoyed a day out at the attraction.

Masked and wielding angle grinders, the gang parked up their scooters outside the Apollo Gallery (Galerie d’Apollon), home to jewels belonging to Napoleon Bonaparte, his wife Josephine and a string of subsequent Emperors and Empresses.

They then extended a freight elevator, resembling a giant ladder, from the back of a flat-bed truck and propped it up against the wall of the gallery, which was opened by King Louis XIV in the 17th Century.

The targeted wing of the Louvre, on the River Seine side of the museum, was undergoing construction work when the gang struck. Employees had previously protested under-staffing at the museum in June.

After scurrying to the top of the ladder, they used an angle grinder to pierce through the museum’s external window, before climbing into the Salle 705 exhibition room.

In a whirlwind seven-minute heist, they prised open two display cases and crammed away nine pieces of the 23-item Napoleon and Josephine Bonaparte collection, Le Parisien reports.

The gang swiped the necklace, pictured, from the sapphire jewellery set of Queen Marie-Amélie and Queen Hortense. It was made in Paris between 1800 and 1835

Empress Eugenie’s brooch, pictured, which contains 2,438 diamonds, was stolen in the raid

The treasures included the Eugénie Crown, adorned with thousands of diamonds and emeralds and worn by Napoleon III’s empress consort Eugénie, which was later found tossed below a window of the Louvre and broken into pieces.

The historic Eugénie Crown, presented to the empress consort in 1855, was sold at auction in 1988 for $13.5million (£10million) before being donated to the Louvre four years later. It is now worth tens of millions of dollars, expert Josie Goodbody told the Daily Mail. 

The gang is also believed to have swiped a priceless necklace and brooch from Salle 705.

By 9.40am they were out of the Louvre, disappearing into the Paris morning on their scooters just as police started to arrive.