WILD dogs mauled and killed four people, including a baby and a teenage couple, whose bodies were found over the past two weeks in a park.
In one case, a teenage girl frantically called her sister with her mobile phone to plead for help as the attack took place.
Neighbours first found the bodies of a 26-year-old woman and a one-year-old child in the area on December 29, authorities in Mexico City said.
The woman, Shunashi Mendoza, was missing her left arm, and prosecutors said that both she and the boy had bled to death and been partially eaten.
On Friday visitors to the same park in the Cerro de la Estrella, a partly wooded hilltop surrounded by the city's poor, found the bodies of a teenage couple who had also bled to death.
"Experts have established that due to the gravity of the wounds, at least 10 dogs were involved in each attack," Mexico City prosecutors said in a statement.
In the second attack, Alejandra Ruiz (15) and her boyfriend Samuel Martinez (16) had gone to the park on Friday afternoon.
The girl called her sister Diana Ruiz pleading for help.
"Several dogs are attacking us, help me!" the girl screamed. The call then stopped.
Miss Ruiz told Milenio Television she thought her sister was joking and still doesn't believe her sister was killed by dogs despite the call.
"What kind of dog can tear the skin from your whole arm and leave just bone and if it was an attack dog why didn't it attack her neck?" Ruiz asked. "What's most shocking is one of her breasts was mutilated."
She said she later visited the place of the attack and saw no pools of blood. "There needs to be a thorough investigation," she added.
Antemio Maya, president of the Street Dog Protection association in the City, also doubts that dogs could have killed the people found in the park. "It's not the behaviour of street dogs to kill humans," Maya said.
Maya said authorities should focus on sterilising pets and educating people about pet ownership instead of spreading the idea of killer animals.
"The authorities trapped beagle, Maltese, poodles; how long it would take for them to kill a person?" he asked.
"A lot of people get tired of their dogs and they simply throw them on the streets," he said. "This is going to create a terrible hate for street dogs."