Officers were called to the 3800 block of Eunice Avenue in the community of Dunlinden Acres around 9:20 p.m. Sunday.
Police say the homeowner, a separated father of five, discovered a decomposing fetus in a shoebox under the bed belonging to his 15-year-old daughter.
"A family member found the infant in a shoebox and someone in the house called 911 to report the incident," Officer Tracey Duffy of the New Castle County Police Department said.
A family relative tells Action News, the teenager had been isolating herself from the rest of the family for months, staying mostly in her room when she came home from school.
The girl went to visit her mother last night; the father entered the room to clean it and made the gruesome discovery.
The relative says the father knew nothing of the pregnancy and the birth until last night.
"We did determine the 15-year-old is the mother," Duffy said.
Duffy says the investigation is continuing to determine additional details regarding the death of the child.
Autopsy results are pending.
It will be up to the Attorney General to determine any charges.