The child's body was found by two fishermen beneath a layer of concrete along the River Raisin in Rainsinville Township, the Detroit Free Press reported Wednesday.
Capt. Michael Thomas, director of the State Police forensic division, says it will take weeks to analyze evidence taken from the gravesite.
"There's someone out there who might have killed a little girl," says Thomas. "She is the top priority."
Two convicted sex offenders out on parole who had been labeled as persons of interest in the case have been sent back to prison to finish their original sentences, says the Michigan Department of Corrections.
Family members gathered Tuesday evening in the Monroe apartment where Navaeh lived with her mother, Jennifer Buchanan and her grandmother and legal guardian, Sherry Buchanan.
Funeral services will be held Saturday.