A male pygmy sperm whale that stranded off the Florida Keys died Wednesday, despite rehabilitation efforts.

Volunteers were preparing the 10 1/2-foot-long whale for an endoscopy, but the animal unexpectedly died before the procedure began, according to Robert Lingenfelser, president of the Marine Mammal Conservancy.

Officials don't know why the roughly 1,000 pound whale died or stranded in the first place. They have been performing tests since finding him Saturday.

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