Thousands of flesh-eating piranhas have been attacking swimmers off a river beach in western Brazil - with at least 15 people suffering injuries.The creatures have infested the waters of the Paraguay river off the city of Caceres\' Daveron beach, in Mato Grosso state.Officials say it is the first time they have had a problem with piranhas in the area, where the aggressive fish began schooling about two weeks ago.Elson de Campos Pinto, 22, was among those attacked.Everyone knows there are piranhas in the region and have always taken the necessary precautions. What is different this time is that they\'ve appeared where they never appeared before.\"I took a dip in the river and when I stood up, I felt pain in my foot,\" he told Globo TV\'s G1 website.\"I saw that I had lost the tip of my toe. I took off running out of the river, afraid that I would be further attacked because of the blood. I\'m not going back in for a long time.\"Firefighter Raul Castro de Oliveira told G1: \"People have got to be very careful. If they\'re bitten, they\'ve got to get out of the water rapidly and not allow the blood to spread.\"City officials say they have no plans to close the beach as it is an important draw for tourists in Brazil\'s Pantanal region, which is known for its ecotourism.Gonzaga Junior, a spokesman for the city government, said: \"Everyone knows there are piranhas in the region and have always taken the necessary precautions.\"What is different this time is that they\'ve appeared where they never appeared before.Despite the reassurances, it is reported the city has seen far fewer people than normal using the beach recently.Large signs have been put up warning swimmers about the piranhas, reading in blood-red letters: \"Attention swimmers. Area at risk of piranha attacks. Danger!\"