Marine experts believe that a humpback whale found Monday evening on a Fire Island beach died after colliding with a ship.

The Riverhead Foundation conducted a necropsy of the 28-foot juvenile male whale Wednesday morning with assistance from the Fire Island National Park Service, Brookhaven Town and bay constables. Biologists found blunt force trauma and a broken skull, injuries consistent with a ship strike, group spokeswoman Rachel Bosworth said.

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A passerby found the carcass in the surf about 8:30 p.m. Monday at Ocean Ridge on Fire Island, near Davis Park.

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The whale probably died a few days ago, Bosworth said. Following the necropsy, officials buried the whale on the beach.

A second whale carcass discovered Tuesday morning in Westhampton Beach is expected to undergo a necropsy Thursday morning. That whale, a True's beaked whale, was taken to the foundation's Riverhead research facility Tuesday afternoon.