MEXICO CITY (AP) -- A 15-year-old girl found fatally bitten by dogs outside a Mexico City park in mid-December may have been the first victim of a feral pack suspected of killing at least four other people over the last month, prosecutors said Wednesday.

Authorities began capturing dogs in the park this week after a mother and her infant boy were found dead and covered in dog bites on Dec. 29 and the bodies of a teenage couple were found covered in fatal bites from as many as 10 dogs a week later.

The four were believed to have been the only victims until the mother of 15-year-old Ana Gabriela Nataret Ramirez told Milenio Television lateTuesday that their daughter had died in hospital after being found covered with apparent dog bites near the Cerro de la Estrella park in the poor southeastern Mexico City district of Iztapalapa on the night of Dec. 16.

The city prosecutor's office confirmed the details of the case Wednesday and said it was looking into whether her case was connected to the other deaths.

"An autopsy revealed that the victim had multiple injuries and puncture wounds on both arms," the prosecutor's office said. "After the events of recent days, the Mexico City district attorney's office broadened the investigation and confirmed the possibility of a new case of homicide resulting from wounds caused by dogs."

Animal control officers swept the park for feral dogs again Wednesday after capturing at least 33 animals over the last two days, borough president Jesus Valencia told reporters at the pound where the animals are being kept.

In addition to rabies, the dogs have been tested for traces of human blood and DNA in order to determine if they were involved in the killings. Valencia said the rabies tests had all come back negative, and the prosecutors' office said the other tests were pending.

He said the borough was helping pay funeral costs for the victims and get psychological help for the relatives.

Many family members have expressed skepticism that dogs could have killed their loved ones, saying their injuries appeared too devastating to have been the result of dog bites.

Valencia said that the borough planned to allow people to adopt any dogs not involved in the killings.

After authorities released photos of the captured dogs, activists started an online campaign protesting the animals' innocence and calling for authorities not to euthanize them. Tens of thousands of dogs are euthanized each year in Mexico if they are captured by animal control officers and not claimed within 72 hours.

Many people re-posted the images of the dogs staring sadly from behind bars at an animal shelter, and the hashtag for the campaign briefly became the top trending topic on Twitter in Mexico.

Mexico City Mayor Miguel Angel Mancera said his government would launch a new program to spay and neuter dogs in order to reduce the number of animals in the street, sending 25 mobile surgical units to neighborhoods where residents would be encouraged to take advantage of free sterilization for their pets.

_____

Adriana Gomez Licon on Twitter http://twitter.com/agomezlicon

Michael Weissenstein on Twitter: http://twitter.com/mweissenstein