The child's mother, Casey Anthony, is in jail, suspected of killing her daughter.
Caylee was 2 years old when she went missing in June. She and her mother shared a house with her grandparents, George and Cindy Anthony, less than a quarter mile from where the bones were found.
Detectives did not give details about the bones found over the weekend but continued to sift through dirt in a wooded area, The Orlando Sentinel reported.
An Orange County water-meter reader found the skull and other remains in a black plastic bag on Nov.11, the first major break in the case in months.