The first litter of Mexican gray wolf pups to be born via artificial insemination was unveiled at a Mexico City zoo Wednesday, as part of an effort by officials to reintroduce this endangered subspecies to its natural range.

The two pups were born May 26 at Mexico City's Chapultepec Zoo, an event the zoo's director Juan Antonio Rivera said was "the first litter of an endangered species obtained in our country by artificial insemination," The Associated Press (AP) reported.

Mexican gray wolves are one of the most endangered species in the country, after excessive hunting brought their population numbers to dangerously low levels three decades ago. Zoo officials described the recent birth of the endangered animals as a "worldwide success," according to BBC News.

Experts say the genetic material for the effort was taken from two wolves in captivity, Ezita, a female from a zoo in Tamatan, Mexico, and Perkins, a male from the Endangered Wolf Center in Eureka, Missouri. Artificial insemination was used in the effort because the mother, already 11 years old, could not conceive through natural means owing to certain physical problems.

In July, Mexico announced the birth of the first known litter of wild-born Mexican pups from a pair of wolves re-introduced in the wild, a project that began in 2011.

The Mexican gray wolf was almost wiped out in the US Southwest by hunting, but also by trapping and poisoning. The last five known animals to survive in the United States were captured in the late 1970s and bred in captivity.

As of January, according to a survey by the US Fish and Wildlife Service, there are 83 Mexican grey wolves living in the wild in Arizona and New Mexico.

Though efforts are clearly being made, the Mexican gray wolf remains an endangered species in the United States and Mexico.