The cause of the fire in mountainous area of Naples is not known, but authorities said they have not ruled out arson.
Farms, homes and a high-voltage electrical network are at risk, ANSA reported.
The fire near Vesuvius National Park is producing smoke that can be seen from several miles away.
The smoke is affecting visibility on the highway between Naples and Salerno, ANSA said.
Authorities also said they have charged a 24-year-old man with arson for starting a blaze that threatened parts of Sardinia earlier in the summer.
Mirko Morle allegedly started a fire that began in June and destroyed more than 1,235 acres of land in Sardinia, ANSA said.
Investigators said they are still searching for other people involved in the crime.
Beyonce flaunts bikini body, Blue Ivy in vacation pics
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'