A 21-year-old sea lion named Holly was found beaten to death in her enclosure in the Dortmund Zoo and police are looking for suspects.

Zoo director Frank Brandstaetter told the dpa news agency Monday that the sea lion, who had been a crowd favorite, was found by workers Friday morning. The other six sea lions in the cage were unharmed and Brandstaetter said keepers had initially thought Holly had died accidentally until they saw the severity of her injuries.

Police say an autopsy found the animal's skull was smashed and she was missing three teeth.

A hole was found in a fence near the sea lion cage but police say so far they don't have any suspects in the attack.