The vicious creatures, known as palometas, have been attacking bathers since Thursday at the Parana River in Rosario, which is 186 miles north-east of Buenos Aires.Seventy people were bitten by the shoal of meat-eating fish in late December as they attempted to cool off from the unusually high summer temperatures.During that attack, a seven-year-old girl lost part of a finger, while other swimmers suffered deep cuts to their ankles, fingers and hands.Palometas have been described as 'a type of piranha, big, voracious and with sharp teeth that can really bite.'They have been known to target humans in Rosario before, with 40 swimmers hurt during a mass-attack in 2008.Media reports said the latest injuries include a boy who suffered a foot wound while floating in the river.Experts say a combination of hot weather and lower numbers of species such as caiman, which prey on the fish, could be causing the attacks.Fatalities are however rare, with the majority of attacks occurring as nips and bites to the extremities, such as hands and feet.(dailymail.co.uk)ANN.Az