The U.S. Fish and Wildlife Service said three of the nine Mexican gray wolves reported dead so far this year were shot illegally in Arizona or New Mexico, The Arizona Republic reported Friday.

Mexican gray wolves are protected in the Southwest under the Endangered Species Act.

"I am disturbed that there are suspicious circumstances around their deaths, and I want to know what happened to each wolf," Benjamin Tuggle, Fish and Wildlife Southwest regional director, said of the three slain predators. The agency is offering a $10,000 reward for information leading to the killer or killers.

The service said two other wolves were killed in traffic this year and a third died of natural causes, leaving behind a pair of cubs that did not survive without their mother.