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The works stolen were Picasso’s Cubist Pigeon aux Petits Pois, Matisse’s La Pastorale, Braque’s L’Olivier près de L’Estaque, Léger’s Nature Morte au Chandelier and Modigliani’s La Femme à l’Eventail.

Paris Mayor Bertand Delanoë has admitted that museum authorities had been aware since March 30 that the alarm system was not working properly in certain rooms, but that the spare parts needed for repairs had not been delivered.

Video surveillance cameras were, however, operating, and – although the museum’s three night-time security guards apparently saw nothing – have revealed the presence of a hooded man inside the building. He is thought to have entered the museum through a window after breaking a padlock, before cutting the canvases from their frames and rolling them up.

Police have noted inadequate protection of Paris museums on several occasions recently, but this is thought to be the most serious heist in French museum history, and follows the theft of an album of Picasso drawings from the Musée Picasso in June 2009.

The theft was discovered before the museum opened on May 20, and the museum was closed for the day as police launched their investigation.

France’s over-worked Office Central de la Lutte contre le Trafic des Biens Culturels (currently pondering more arrests in the Drouot Cols Rouges scandal) has been put in charge of the case, and immediately posted images of the stolen works on its Treima database (which contains 80,000 stolen artworks).

The stolen pictures have also been listed on the smaller Interpol database. Sources say the ‘sophisticated’ theft is probably the work of organised crime, and that the pictures may have been taken with a ransom in mind, or to exchange for arms or drugs, as they will be impossible to sell on the market.

The much-touted £90m valuation of the five pictures would doubtless be conservative were they ever offered for sale legitimately, but their black market value would be negligible.

The Paris Modern Art Museum – which has no connection with the Pompidou Centre – opened in 1961 and owns 8000 works, mainly French paintings and sculpture from the first half of the 20th century.

It also stages major temporary exhibitions. Its most spectacular permanent exhibit is Raoul Dufy’s La Fée Electricité which, at 33ft 10in x 203ft 5in (10 x 62m), takes up a whole room and is probably thief-proof.

By Simon Hewitt