More than 70 people were injured in a piranha attack that took place on Christmas Day in the Argentine city of Rosario, officials said Thursday.

The feeding frenzy took place mid-morning on Wednesday in the Parana River, known to be populated with the carnivorous fish. A recent heat wave brought thousands into the infested waters, where many were injured and a 7-year-old girl lost part of her finger, Agence France-Presse reports.

"There were some people that the fish literally had torn bits of flesh from," Gustavo Centurion, a medical official, said.

Officials say the unseasonably warm weather, with temperatures soaring above 100 degrees Fahrenheit in the region, brought the fish to the water’s surface and triggered the attack. There is also speculation the fish were attracted to the area by bait left by local fisherman.

Witnesses say swimmers suddenly began to run out of the water, screaming, bleeding and crying for help, La Capital newspaper reports. More than 20 children were injured. One boy reportedly fractured his hand. Others had bites to their feet and hands, the Independent reports.

"This is not normal," Federico Cornier, the director of emergency services in the city of Rosario, told Al Jazeera, adding that the fish were "palometas," a relative of the piranha. "It's normal for there to be an isolated bite or injury, but the magnitude in this case was great. This is an exceptional event."

Piranha, a freshwater fish of South America, range in size from about 8 to 18 inches long and are known to attack any living animal that enters the water they inhabit. Their triangular-shaped teeth are razor-sharp, able to chop prey into tiny bits. The carnivorous fish rarely attack people and usually swim alone, making the latest attack in Argentina unusual, according to local government spokesman Ricardo Biasatti.

Argentinean officials say piranhas are attracted to blood. Once one of them draws blood, more are drawn to the area and attack others, La Nacion reports.

The city of Rosario is about 300 miles north of Buenos Aires.

Argentina