Colorado Parks and Wildlife said the death of a female gray wolf last weekend in Rocky Mountain National Park is currently under investigation.

A collared gray wolf released in Colorado in January as part of the state’s historic reintroduction effort died in Rocky Mountain National Park this week, wildlife officials said Thursday.

CPW and the National Park Service confirmed the wolf died inside the boundaries of RMNP, and said that the U.S. Fish and Wildlife Service will conduct a necropsy and other investigative efforts because gray wolves are federally listed under the Endangered Species Act.