Neopolitans rushed to the phones, jamming switchboards at the city's eruption hot line with calls until they realized the noise was caused by Italian F-16s breaking the sound barrier while scrambling to intercept an unidentified aircraft, the Italian news agency ANSA reported.

Naples goes through Mount Vesuvius scares fairly often, the news agency said. The last major scare was in August 2007 after the U.S. magazine National Geographic claimed Naples' evacuation plans wouldn't get people out in time if Vesuvius erupted as it did in A.D. 79, burying the city of Pompeii.

Vulcanologist Franco Barberi told ANSA that even in the worst-case scenario, Naples' evacuation plan would allow its population to be smoothly evacuated during an eruption.