A dolphin was found dead in the Hutchinson River near Mount Vernon, police said Saturday.
Westchester County police learned of the dolphin near Glover Field on Friday afternoon, spokesman Kieran O'Leary said.
They removed the dolphin's body from the river and stored it overnight, O'Leary said.
The state Department of Environmental Conservation took the body on Saturday and will perform a necropsy, O'Leary said.
Ocean creatures occasionally make their way into tri-state rivers.
A whale was spotted in the East River on New Year's Eve.
In November, a humpback whale got stuck on a sandbar in Moriches Bay, east of New York's Hamptons, and was euthanized.
Around the same time, a humpback whale cavorted in the Hudson River for nearly a week, with sightings reported from the Statue of Liberty to well north of the George Washington Bridge. Scientists suspected it was chasing food in the cleaner river.