PLYMOUTH (CBS) – The pilot whale that recently swam into Plymouth Harbor has now died.

New England Aquarium staff members attempted to euthanize the whale Thursday night, but after a staff veterinarian administered a sedative to relax the mammal, it died naturally.

Aquarium authorities suspected something was wrong with the whale, which was showing signs of serious distress and should not have been this far north. Usually, short-finned pilot whales aren’t seen north of New Jersey.

The aquarium is now testing the whale’s remains to see what made it so sick.

The skeleton will be donated to a museum.