Rangers hiked for miles to confirm the deaths of two people who were camping at an island national park in Michigan’s Lake Superior

Rangers hiked 11 miles (17.7 kilometers) overnight to confirm the deaths of two people who were camping at an island national park in Michigan’s Lake Superior, authorities said Tuesday.

“The causes of death are unknown at this time. … The incident is currently under investigation,” Isle Royale National Park said in a statement.

Two rangers set out Sunday night after park staff was informed that two people were dead at a remote campground. They reached the site Monday.

A phone message left with park authorities seeking more information Tuesday was not immediately returned.

Isle Royale is an extraordinary wilderness park, accessible only by ferry, personal boat or seaplane and only open six months a year due to extreme weather.

The island’s population of moose and wolves is regularly studied by wildlife scientists.