Updated

Italian prosecutors on Tuesday opened a criminal investigation into the deaths of at least 10 people swept away by a flash flood as they hiked through a narrow gorge in the southern region of Calabria.

Italy's civil protection agency said at least three people were missing, although the number could be higher since guides were not mandatory inside the Raganello Gorge, a popular spot for aquatic trekking.

Rescue workers saved 23 people Monday after some 2 ½ meters (8 feet) of rain filled the narrow gorge, which features rock faces as high as 700 meters (2,300 feet). Eleven people were hospitalized, including a 10-year-old boy treated for hypothermia.

Prosecutor Eugenio Facciolla said authorities were investigating possible charges including manslaughter, causing bodily harm and official negligence, the news agency ANSA reported. No target has been identified.

TV images showed helmeted rescue workers holding survivors as they were brought to safety on ropes.

Pasquale Gagliardi, a doctor with an emergency helicopter service, told ANSA that another survivor was an 8-year-old girl, found in a state of shock next to a body. Her parents were believed to be among the dead.

The victims were among two groups of trekkers on an excursion in the 12-kilometer- (7-1/2 mile-) long gorge, inside the vast Pollino National Park.

Search operations continued through the night, and the head of the civil protection agency in Calabria, Carlo Tansi, said one of the bodies was found five kilometers (three miles) from the flooded area.

A local resident who helped respond to the emergency, identified only as Claudio, told ANSA that he helped two youths from Naples, who managed to climb out of the gorge on their own.

"They were in a state of shock and they arrived without shoes and with cuts from the rocks. They recounted a terrifying situation," he said.

The gorge boasts aquatic trekking along the stream that cuts through the massive rock, where hikers pass by waterfalls and natural slipways.

Guides typically supply helmets, wet suits and other equipment.