A swarm of carnivorous fish attacked more than 70 swimmers at a popular beach in Argentina on Christmas Day, a medical official said on Thursday. 

Seven children lost part of their toes or fingers in the attack, and a seven-year-old girl had to have her finger partially amputated. Dozens more suffered bite wounds from the flesh-eating fish, according to Reuters. 

The attack occurred when thousands of people were swimming in the Parana River near Rosario, which is about 180 miles from Buenos Aires.

"This is not normal," said Federico Cornier, the director of emergency services in the city of Rosario. "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." 

Cornier said that the fish are relatives of piranhas called "palometas." He said they are "a type of piranha, big, voracious and with sharp teeth that can really bite." 

The beach was exceptionally crowded because many Argentines were seeking respite from the heat wave that occurred over the holiday. 

Although Cornier called the event "exceptional," Ricardo Biasatti, sub secretary of Natural Resources for the province of Santa Fe, said the incident was "isolated and insignificant" compared to the size of the river. 

According to CNN, Julian Aguilar, president of a local fisherman's group, said the likelihood of a similar event occurring is low, because the attacks on humans by that type of fish are "occasional."