The Tualatan Wildlife Refuge, which was built in the 1950s and is home to endangered wolves, was shut down by authorities Wednesday, after an investigation found the building was unsafe and that it was unsafe to visit.

The refuge was closed by the California Department of Fish and Wildlife due to a health and safety concern, a spokeswoman for the department said.

The refuge has been closed for over a year and the wildlife refuge is now under quarantine, the department’s statement said.

A spokesman for the U.S. Fish and Game, Scott Rochon, said that the refuge has received approval to reopen for hunting.