The Detroit Free Press reports Tuesday that part of the man's leg was chewed off. The badly decomposed body was found Monday afternoon on the city's northwest side by relatives.
Sgt. Michael Woody says the body's condition makes it difficult to determine if he died of natural causes or from foul play.
Woody also says investigators aren't sure if a dog or another animal gnawed on the remains.
Thousands of stray dogs reportedly roam Detroit's streets, living in vacant houses and buildings. But raccoons, opossums and other wild creatures are finding refuge in the city which has lost more than one million people since the 1950s.