MEXICO CITY – Police scoured a hilly urban park for feral dogs and tested dozens of captured animals on Tuesday in a hunt for those responsible for four fatal maulings.

Authorities have captured 25 dogs near the scene of the attacks in the capital’s poor Iztapalapa district, but rather than calm residents, photos of the forlorn dogs brought a wave of sympathy for the animals, doubts about their involvement in the killings and debate about government handling of the stray dog problem.

Activists started an online campaign protesting the dogs’ innocence and calling for authorities not to euthanize them.

The hashtag for the campaign became the top trending topic on Twitter in Mexico by midday Tuesday, with some users furiously accusing the authorities of cruelty to animals and others sarcastically calling the dogs “political prisoners” and mocking the fuss over the fate of the animals.

Officials said they were testing the captured dogs’ fur for blood, and examining their stomach contents to determine if they were the killers of the four people whose bodies were found covered in dog bites in two separate incidents in recent days.

Neighbors of the Cerro de la Estrella park found the bodies of a 26-year-old woman and a 1-year-old child in the area on Dec. 29, authorities said. The woman, Shunashi Mendoza, was missing her left arm, and prosecutors said that both she and the boy had bled to death.

Then on Saturday visitors to the park found the bodies of Alejandra Ruiz, 15, and her boyfriend Samuel Martinez, 16, who had gone to the park and were found dead from blood loss.