Director of lifeguards Federico Cornier said Thursday that thousands of bathers were cooling off from 38 degree temperatures in the Parana River in Rosario on Wednesday when bathers suddenly began complaining of bite marks on their hands and feet. He blamed the attack on palometas, "a type of piranha, big, voracious and with sharp teeth that can really bite."

Those injured in the frenzy by the sharp-teethed fish included a girl who lost part of a finger, Health Undersecretary Gabriela Quintanilla told reporters on Thursday.

A medical official, Gustavo Centurion, said it began mid-morning on Christmas Day and was ‘‘very aggressive.’’‘‘There were some people that the fish literally had torn bits of flesh from,’’ he said. Paramedic Alberto Manino said some children he treated lost entire digits.

Ms Quintanilla said the incident occurred off the coast of Rosario, some 310km north of Buenos Aires.

The region has been hit by a heat wave with temperatures soaring to some 38 degrees prompting thousands to seek relief in the waters of the Parana River, which is packed with carnivorous fish.

Officials said the unusually warm weather also was apparently responsible for the fish congregating on the river’s surface.

Mr Manino told the Todo Noticias channel that city beaches were closed, but it was so hot that within a half-hour, many people went back to the water.

AP, AFP