Incident comes days after another tourist carved initials into Rome monument.
A 17-year-old Bulgarian student who defaced the Colosseum has been reported by Rome police for aggravated damage to a building of historical and cultural interest, with a report of the incident sent to the city's public prosecutor's office.
The tourist was visiting the Colosseum on a school tour on 28 April when she decided to engrave the letter "M", the intital of her first name, on an interior ground-floor wall of the monument before being caught by security staff who called the police.
The incident came three days after an Israeli tourist carved the initials of the names of her husband and children into an internal pillar of the ancient amphitheatre.
In recent years there have been a string of similar cases including that of a Bulgarian footballer who told police that he presumed it was alright to add his initials to the graffiti already present.
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Bulgarian student defaces Colosseum in Rome
00184 Rome, Metropolitan City of Rome, Italy