A fresco pinched from a Roman villa near Pompeii over 30 years ago has been recovered by police in a major operation into stolen artwork and artefacts, it was revealed on Tuesday. Experts believe the fresco was completed during the 1st century AD and probably came from the villa of Poppaea Sabina, Emperor Nero's second wife. The fresco was tracked down during a lengthy Italian-led international investigation, which has resulted in trafficking and fraud charges against 31 people in Italy, France and Switzerland. Operation Ulysses has uncovered a haul of more than a thousand archaeological finds and a series of outstanding Impressionist forgeries.

The probe was opened three years ago after Italian officers started looking into a series of illegal excavations in different parts of Lazio, Sardinia and Tuscany, in an area once home to the Etruscans. The trail initially led investigators to Milan and then eventually abroad, first to Switzerland and later onto Paris. The fresco was finally tracked down to an elegant house in the French capital.

Police say the artwork was snatched in the 1970s from a villa that stood in the Ancient Roman coastal resort of Oplontis, close to Pompeii. Oplontis, which is near the modern-day town of Torre Annunziata, was one of the settlements worst hit by the AD 79 eruption of Mt Vesuvius.

The fresco was originally a wall decoration and shows a landscape with temples, gardens, fountains, a Greek assembly place and a walled residence. Of the thousand-plus antiquities recovered, police say around 400 are worth several thousand euros each. Among the haul are 87 ancient masterpieces from Greece, Tuscany and southern Italy, including a brightly coloured mosaic of a young freedman. Investigators say the trade in stolen antiquities reaped traffickers at least three million euros in profits over the years. They also discovered several outstanding Impressionist forgeries in a Milanese house, used as collateral for hefty bank loans. The 22 fakes included a Monet and a Degas.

A selection of forged paintings from great 20th-century Italian artists, such as Giorgio De Chirico, Mario Schifano and Lucio Fontana, were also used to raise credit, police said. Operation Ulysses is the latest in a series of successful investigations over recent years, part of Italy's efforts to crack down on antiquities trafficking. As well as reclaiming several major hauls, Italy has signed landmark deals with foreign museums and galleries including the Metropolitan Museum of Art in New York, Princeton University and the Boston Museum of Fine Art to return allegedly plundered art.

In the first case of its kind, Rome is also trying former Getty curator Marion True and an American antiquities dealer, Robert Hecht, for knowingly acquiring smuggled artefacts.