KLAMATH FALLS, Ore. — Another gray wolf has been found dead in Oregon, marking the third such unsolved death of a federally protected wolf in the past year, state and federal wildlife officials said. Another wolf was shot by a hunter who claimed self-defense.

The wolf was found dead Oct. 29 in Klamath County on state forest land. The U.S. Fish and Wildlife Service has offered a $5,000 reward for information on the killing, authorities said Monday.

The wolf was known to biologists as OR-25 and was wearing a tracking collar. It was believed to have killed a calf at a private ranch near Prospect earlier this year, according to state wildlife officials.

OR-33, another collared male, was found shot dead April 23 about 20 miles northwest of Klamath Falls in Fremont-Winema National Forest. OR-28, a collared female, was found dead Oct. 6, 2016, in Fremont-Winema National Forest near Summer Lake.

All three investigations remain open, and authorities do not believe the latest wolf died of natural causes, Oregon Department of Fish and Wildlife spokesman Brent Lawrence told the Mail Tribune .

Killing gray wolves in the western two-thirds of Oregon is a violation of the federal Endangered Species Act and of Oregon state game laws. The federal offense is punishable by up to a $100,000 fine, a year in jail or both. The maximum state penalty is a fine of $6,250 and a year in jail.

Wolves in Oregon hunt deer, elk, bighorn sheep and goats. But they also can target livestock and are loathed by many livestock owners.

State wildlife officials say 141 livestock or domestic animals have been killed by wolves in Oregon since they began returning to the state in the late 1990s.

In 2016, wildlife officials estimated a minimum of 112 wolves lived in Oregon in 11 packs that included eight breeding pairs.

An elk hunter recently shot and killed a gray wolf in eastern Oregon in self-defense after he said the wolf charged at him while he was hunting alone and he mistook it for a coyote. The hunter, who contacted authorities after realizing he had shot a gray wolf, will not be prosecuted because the shooting was ruled self-defense.