A group of fishermen summoned police to River Drive near Linwood Avenue at 11:20 p.m., Police Chief Michael Foligno said.
"They pointed to what appeared to be a body floating face down in the river near the eastern river bank," he said.
He apparently was in his 20s, Foligno said.
The Bergen County Medical Examiner's Office took the body in an attempt to identify it and how the man died.
Borough firefighters also responded, as did the Bergen County Sheriff's Bureau of Criminal Identification.
Anyone who can help identify the man or how he ended up in the river is asked to contact Elmwood Park police: (201) 796-0700.
Callers may remain anonymous, the chief said.
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