The 23-year-old man from Baltimore tried to retrieve his cell phone at the time. He was walking on an unauthorized path along with three family members on Saturday morning when the incident happened, the Carabinieri of the Provincial Command of Naples revealed.
Two British tourists were also seen walking the forbidden path.
Remarkably, after the fall, the man reported only a few bruises on his hands, arms and back.
He was treated at the scene by an ambulance.
However, he insisted he did not want to go to the hospital, according to police.
The path he was walking on had clear signs warning that entry was prohibited, authorities added.
They also added that the prosecutor will decide whether to charge for an invasion of public territory.
However, according to The Guardian, citing local press reports, the man was taking a selfie when his phone fell from his hand and into the volcano.
He then went down into the crater before falling several meters and losing his balance.
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According to the national park’s website, the crater has a diameter of 450 meters (1,476 feet).
It is also 300 meters (984 ft) deep.
Vesuvius had been a dormant volcano for centuries before a spectacular eruption in 79 AD buried cities such as Pompeii, Oplontis, and Stabiae.
Pompeii was covered under a 23-meter-deep layer of volcanic debris, which protected the ruins from the damaging effects of weather and climate.
It has become a popular tourist destination as well as an important site for archaeologists.