Six Mexican gray wolves, a species on the brink of extinction, were born in a nature reserve in the northern state of Sonora, a state environmental official said.

"The birth of these pups is a big accomplishment for the conservation of an extinct species in its natural habitat," Sonora Environmental Commission director Oscar Tellez told Efe.

The Mexican gray wolf (Canis lupus baileyi) is a subspecies that has "difficulty reproducing in captivity," Tellez said.

The pups are the offspring of "Wuera," who was brought to the park in 2008 from a zoo in the central state of Guanajuato, and "Federiko," who arrived at the reserve in 2012 from a state park in New Mexico.

The pups were probably born last month, but no one spotted them until the female moved them to a new den, experts said.

Nine pups were born, but three "died from natural causes," Tellez said.

The Mexican Wolf once roamed across a vast region, including parts of the present-day northern states of Chihuahua, Coahuila, Nuevo Leon and Durango; the central states of Zacatecas, Aguascalientes and San Luis Potosi; and the southern state of Oaxaca.

The subspecies had been categorized in recent years as "probably extinct in the wild," the government says. EFE