International art experts have been called in by Italian police to authenticate what appears to be a Modigliani painting left in a staff lavatory next to customs at Bergamo airport.

The painting was found wrapped in a sheet and packed inside a box. “It was ready to be slipped through airport controls on to a plane,” a police spokesman said. One theory is that it was abandoned by a smuggler who lost his nerve.

The painting, measuring 35cm (14in) by 25cm, is thought to be from a private collection. If genuine, it would be worth at least €1 million (£670,000). It is being held by the Carabinieri art theft squad in Monza.

Art dealers said that no Modigliani painting would have been given an export licence by the Ministry of Culture. A campaign is under way to reclaim Modigliani, who was from Livorno but spent most of his short life — he died in 1920 aged 35 — in Paris, with a Modigliani memorial museum planned for Rome. The Rome project is backed by the Modigliani Legal Archives in Paris, the principle foundation for the preservation of his legacy.

Police said that the apparent attempt to smuggle the painting from Bergamo “could be part of a much wider smuggling operation”. The painting was found by airport staff, who at first thought they were dealing with a “suspicious package”.

The painting is believed to be a portrait of Rosalie Tobia, an Italian woman painted many times by Modigliani in Paris.

One celebrated portrait of Rosalie is held at the Brera Pinacoteca in Milan. Curators said yesterday that their painting was still at the Brera and had not been stolen. However, other portraits of her are in private collections.

Rosalie, who began as an artists’ model, later ran a dairy-cum-restaurant in Montparnasse, “playing mother to the poverty-stricken artists whom she nourished” with pasta and minestrone. The art world urged caution yesterday over the Bergamo discovery. Osval-do Patani, a leading Modigliani expert, told The Times that he had yet to see the painting. “There are a lot of fakes about,” he said.

In 1984 the city council in Livorno dredged a canal because of a local legend that Modigliani had tossed some sculptured heads into it as a young man. Three sculpted heads were found — dubbed Modi 1, 2 and 3 — and were hailed as a big find. It emerged that art students had carved one and a dockworker had made the other two.

This month a 1918 painting of a girl in a black beret by Modigliani, Jeune Fille au Beret, fetched £6.1 million at a Christies auction in London. The successful bidder, an unidentified woman, paid £2 million more than the estimate. The seller was an heir of the Paris collector Jonas Netter, who paid about Fr300 apiece for Modigliani canvases early last century.

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