U.S. wildlife managers say their counterparts in Mexico have released two pairs of endangered Mexican gray wolves south of the U.S. border as part of an ongoing reintroduction effort.
The wolves came from the Ladder Ranch in southern New Mexico and were placed in two areas in the state of Chihuahua.
Officials say the wolf population in Mexico now numbers about 45.
In the United States, releases of wolves have been taking place in Arizona and New Mexico for two decades.
The most recent count showed at least 186 wolves in the wild in the two states.
The results of a new survey are due soon.