Border agents discovered the sand, from the beach of Chia in southern Sardinia, packed into 14 plastic bottles in the trunk of the couple's SUV yesterday as they were about to board a ferry departing from Porto Torres, Sardinia, to Toulon, France.
The pair reportedly said they wanted to take the sand home as a “souvenir” and did not realise they'd committed a crime.
But Sardinia's famed white sand is a protected resource, and removing it from the island is an offence normally punishable by fines of between €500 to €3,000.
Residents have long complained that visitors help themselves to handfuls of the fine white sand on the island's north-east coast – a favourite with holiday-makers – resulting in the loss of tonnes of the precious natural resource each year.
Authorities at Sardinia's ports and airport carry out systematic bag checks to catch passengers smuggling sand.
Airport agents in Olbia confiscate around 2 tonnes of stolen sand a year, according to local news site Gallura Oggi, while another 500 kilos were seized last summer from ferry passengers at the port of Olbia, where checks are less strict.
Over the past ten years they've seized some 10 tonnes, most of it collected in half-litre bottles, according to the director of a marine reserve off Sardinia's north-eastern coast.
But this is the first reported case of somone attempting to take such a large amount of sand home with them.
Some towns around Sardinia, which is home to some of Italy's most popular beaches, have proposed banning towels and large bags in a bid to stop holidaymakers removing sand from the fragile coastline, whether deliberately or inadvertently.
There's a “growing trade” internationally in sand, pebbles, shells and other objects from Sardinia's beaches, with the stolen items often being sold on Ebay, the Corriere della Sera writes.
Some repentant sand thieves have returned sand and shells to the island recently, where it is replaced onto suitable beaches.