(CNN) — We've all been tempted to bring a little bit of paradise home from our holidays. But the urge has backfired on a French couple, who are facing up to six years in prison for removing sand from a beach in Sardinia , where they had been on vacation.

The Italian island's white sand is protected, and tourists face fines and even jail time for removing it from local beaches -- but the couple say they did not realize they were committing a crime.

Police in the northern city of Porto Torres found the sand while making routine checks on cars waiting to board a ferry to Toulon in southern France.

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They spotted some bottles filled with sand through the window of the car, and arrested the couple, a man and woman in their 40s, police told CNN.

Overall, 14 plastic bottles containing around 40 kilograms (88 pounds) of white sand were seized, police said.

The couple were reported to a court in the city of Sassari for aggravated theft and they risk a fine of up to €3,000 ($3,300) and between one and six years' imprisonment.

Police seized 14 bottles containing around 40 kilograms of sand. Guardia di Finanza

Police told CNN that the tourists said they were unaware of the laws about removing sand, but noted that the island's beaches have signs in several languages informing visitors.

Theft of white sand and rocks from Sardinia's beaches is very common, a police officer said, and there is an illegal market for them on the internet.

"The people of Sardinia are very angry with tourists that steal shells and sand, because it's a theft (from) future generations that also puts at risk a delicate environment," the officer told CNN.

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Sand thieves are usually picked up at airports, in bag searches and by scanners.

A Facebook page, "Sardegna Rubata e Depredata" -- "Sardinia, robbed and plundered" -- which was set up by a group of security officials from the island's airports, campaigns against the depletion of Sardinia's beaches.

"The purpose of the page is to raise public awareness about this problem," one of the page administrators previously told CNN Travel.