The man said he had moved the tiles accidentally in an attempt to get a good photograph of the site on Wednesday.
He was taking a picture at the House of the Sailor, which gets its name from the mosaic located at the entryway, which depicts six boats. The 2nd-century, two-storey building was only opened to the public for the first time in autumn 2017 after extensive restoration.
- How Pompeii graffiti gives insight into groups marginalized by history
- Restored Pompeii kitchens give insight into how Romans cooked
- The grim reality of the brothels of Pompeii
Security staff at the tourist hub who saw the incident asked the amateur photographer to explain his intentions to local police, but were satisfied that he had not intended to cause any damage.
"The episode testifies to the fragility of our heritage, and to the constant protection of the site carries out by security and law enforcement officers daily," representatives from the archeological site said in a statement.
They called for "a collective awareness about our common cultural heritage" from each visitor to the park in order to preserve the delicate ruins.
Specialist restorers will reattach the parts of the mosaic that got dislodged.
The House of the Sailor was uncovered in 1871 and contains a private spa and underground bakery workshop, combining aspects of traditional town houses with those of commercial warehouses.
Thefts from Pompeii
While the American's actions may not have been malicious, the site also struggles with tourists who pocket relics as holiday souvenirs or even to sell for a profit.
Sometimes however, the thieves try to make amends. In 2014, a Canadian tourist returned an artefact she had stolen from Pompeii's amphitheatre during her honeymoon - 50 years earlier.
And several thieves have sent back the loot claiming the relics are 'cursed'. Pompeii's archaeological superintendent said in 2015 that he was considering setting up an exhibition of the returned artefacts and accompanying letters, to tell the story behind the stolen pieces.
READ ALSO: How Italy plans to fight back against monument vandals
Photo: Tiziana Fabi/AFP