ALBUQUERQUE, N.M. (AP) — Federal wildlife managers say two endangered Mexican gray wolves have died, bringing the total of dead in the last few months to four.

The animals were found dead in New Mexico in March. Authorities did not release any details about the circumstances or where the wolves were found but confirmed their deaths are under investigation.

The deaths come after two of the animals were discovered dead in Arizona in February. They were the first to be reported this year.

U.S. Fish and Wildlife officials had those carcasses sent to a lab in Oregon for examination.

Efforts to reintroduce the endangered wolves in Arizona and New Mexico have been ongoing for two decades.