The basilica, dating back some 1,900 years, was found during excavations that took place as part of the demolition of a building in the heart of London.
The headless statue is believed to depict Marcus Aurelius. The investigation into its origins comes over a decade after Turkey claimed that 21 objects at the museum were linked to an illicit trade.
The discoveries shed light on what the Italian Culture Ministry calls a "unique multicultural and multilingual haven of peace" between Etruscans and Romans at a time when they were mostly at war.