An American tourist has died after falling suddenly ill on Mount Etna in Sicily, rescuers said.

A 55-year-old American tourist has died after falling ill while hiking on the south side of Mount Etna in Sicily, Italy’s mountain rescue service said Friday.

Rescuers said the cause of his illness was still unknown, but they warned of the danger of high temperatures and humidity, which could be dangerous for tourists who usually have no specific preparation for such trips.

After being alerted on Thursday afternoon, a mountain rescue team and an air ambulance were able to reach the man in a remote area.

Rescuers said attempts to revive him failed and he was declared dead at the scene before his body was taken to the nearest service area for transfer to the hospital morgue.

“Tourists taking part in these trips should not underestimate the risks associated with high temperatures, strong humidity and the sudden jump in altitude,” said Alfio Ferrara, spokesman for the mountain rescue service.

“They often agree to take part in these trips, which reach altitudes of between 2,000 and 2,300 metres (6,500 to 9,800 feet), after spending the day on the beach,” he added.

Ferrara said temperatures on Mount Etna were estimated at between 77 and 82 degrees on Thursday. Italian authorities declared a state of maximum alert in seven cities on Thursday, most of them in central parts of the country.

They warned that the hot conditions were exacerbated by humidity and could affect healthy people as well as those with health problems.

Mount Etna, Europe’s highest active volcano, has seen a significant increase in activity over the past week.