Two campers were found dead in a remote backcountry campground at Isle Royale National Park, according to a news release from the park service.

Rangers received two separate reports Sunday afternoon of two people found dead on the island on Lake Superior, which is part of Michigan. Two park officials hiked 11 miles overnight to the campground and confirmed the deaths of the yet unidentified campers.

The cause of death is not yet known.

Additional ground and aviation resources have responded, according to the news release. The investigation is ongoing.