The carcasses of three wolves “frozen solid” were found dumped in a ditch along a northern Minnesota highway in what conservation officials are confident is a case of poaching, federal authorities said Thursday.

The discovery on Hwy. 8 near Floodwood, about 35 miles southeast of Grand Rapids, was reported on Jan. 22 to a state Department of Natural Resources poachers tip line, according to the U.S. Fish and Wildlife Service (USFWS).

“The wolf carcasses were discovered in a pile in the ditch just off the shoulder of the road, as though someone had driven up and dumped them off the edge of the shoulder,” agency spokeswoman Tina Shaw said.

The gray wolf is currently listed by the federal government as “threatened” under the Endangered Species Act, meaning they cannot be hunted except in defense of human life. A conviction for each violation could result in up to six months in prison and a fine of up to $25,000.

The federal agency announced a reward of up to $2,500 for information leading to an arrest and conviction.

The carcasses were sent to the USFWS’s national forensics lab in Ashland, Ore., the country’s lone crime lab for animals, Shaw said.

“There appear to be marks from a snare on the necks of the wolves, but our forensics scientists are currently making [a] determination” into how the animals were killed, Shaw said.

Shaw added that “evidence supports that the wolves were killed elsewhere and purposely moved to this location … right on the road.”

The federal agent investigating the killings said the animals “were frozen solid and in perfect condition,” Shaw said. “There’s a good chance that they were dumped there the night before they were called in.”

The USFWS is working with the Minnesota Department of Natural Resources (DNR) on the case, Shaw said. Anyone with information about this case is urged to call the DNR’s Turn in Poachers (TIP) line at 1-800-652-9093.

“We really do depend on the DNR tip line,” Shaw said.

Six decades ago, Minnesota’s wolf population fell to a record low of 750. However, the most recent count by the DNR put the number at upward of 2,400.

A judge’s ruling in late 2014 reinstated Endangered Species Act protections for gray wolves in Minnesota, Wisconsin and Michigan and placed the animals under protection of the USFWS. They had been removed in January 2012 from the endangered species list, which briefly allowed for hunting seasons.

Dave Mech, a senior research scientist in Minnesota with the federal Northern Prairie Wildlife Research Center, points to the stable wolf population in the state as evidence that the animal no longer needs to be listed as threatened.

“Their population is secure, and it’s recovered,” Mech said. “I don’t have any reason to believe that it’s threatened or endangered in Minnesota.”

Because wolves have been removed and then put back on the endangered species list, landowners “who live with wolves have become more frustrated,” Mech said. “There’s probably people who take it out on the wolves.”

Also, hunters have complained about wolves contributing to declining deer and moose populations, he added.

While some landowners and hunters want wolves off the endangered species list, a DNR poll in 2012 found that nearly 80 percent opposed the hunting of wolves.