Over 50 animals were poisoned in the city of Esperanza in Santa Fe, Argentina.
Pet and stray dogs and cats, as well as some birds, were found dead at the end of last month with clear signs of poisoning.
Local police authorities started an investigation after pieces of meat with a powerful toxic substance were found throughout the neighbourhood.
“This whole city is very concerned about this,” neighbours said to a local newspaper.
“There’s no doubt a madman is loose committing this gruesome actions. We understand not everyone likes animals, but to unleash this massacre…
“The most terrible thing is that our kids are in danger. Anyone can come into contact with the product and the consequences would be fatal.”
Mariana Weiner, president of the Humane Association of Esperanza, said numerous cases of animal poisoning were reported in a week’s time and one person was identified as responsible but investigations continue.
Weiner said the poison is yet to be determined but symptoms include seizures, vomiting and severe drooling.