Dale County, Alabama Chief Deputy Walter Ford said the male victim's remains were badly decomposed, making it impossible to determine an age, race or injuries.
Dothan Police investigators want to know if the body is that of a missing Dothan man.
Authorities said the body was found around 3:30 p.m. near Dale County Road Nine. The river runs between Dale and Houston counties in southeast Alabama.
Ford said it appeared the remains had been in the water for up to two week. He said state pathologists in Mobile will conduct an autopsy.