FBI agents found the body of Emilliano Terry the day after Camilia Terry, 20, reported her son had disappeared from a park near their home, The (Cleveland) Plain Dealer reported Tuesday.
"We are treating this as a homicide instead of a missing person or abduction," said Police Chief Michael McGrath.
Fourth District Commander Deon McCaulley said Terry changed her story during questioning.
"The statements of Miss Terry became very inconsistent and we decided we would further investigate her involvement in the situation," McCaulley said.
Authorities are awaiting the results of an autopsy to learn the cause of Emilliano's death.
Terry's other two children, boys ages 5 and 5 months old, have been placed in the custody of the Department of Children and Family Services.