Mexico City police rounded up stray dogs in an ecological reserve on Monday after a pack of them apparently killed four people, including a mother and her baby, in recent days, authorities said.

The bodies of the mother and child were discovered with bite marks on December 29, while a young man and woman were found on January 5 at La Estrella Hill in the capital's eastern Iztapalapa district.

The authorities ruled out a deadly robbery since the victims still had all their belongings on them, the public security department said.

The city police's Animal Control Brigade captured 25 dogs, including eight puppies, that were hiding in caves and holes. The operation will continue and include the capital's huge Chapultepec Park.

A 2008 study by the National Autonomous University of Mexico found that three million abandoned dogs roam the streets of the megalopolis.