Authorities are investigating the killing of three gray wolves that were illegally shot last month in northern Minnesota.

The U.S. Fish and Wildlife Service is offering up to $2,500 for information that leads to an arrest and conviction of the shooter or shooters.

The wolves were found together near Floodwood, Minn., along Highway 8, authorities said Thursday.

The gray wolf is protected under the federal Endangered Species Act. Killing a gray wolf is punishable by up to six months in jail and up to $25,000 in fines.

Those with information about the killing can contact the Minnesota Department of Natural Resources Turn in Poachers (TIP) line at 1-800-652-9093

Youssef Rddad is a University of Minnesota student on assignment for the Star Tribune.