An Italian couple and their 11-year-old son died Tuesday after they crossed a fenced-off area and fell into a steaming volcanic crater near Naples, authorities said.

The incident occurred at Solfatara volcano, a part of the Campi Flegrei volcanic tourist area located about 30 kilometers (19 miles) east of Naples.

Super volcano in the Campi Flegrei area near Naples

"Either there was a small explosion, or the ground simply gave way from their weight, and they fell into this hole," national fire brigade spokesman Luca Cari said. "It was inside a fenced-off area."

Local media reported the 11-year-old first crossed the fence and fell into the crater. The couple then fell in as they tried to save him.

Authorities said the three likely died of asphyxiation from deadly gasses.

Another seven-year-old son stayed behind the fence and survived. Authorities found the young boy in a state of shock.

Campi Flegrei area consists of multiple volcanos.

cw/rc (AFP, Reuters)