Police and firefighters were called around 4:15 a.m. Wednesday to a home on a report of an infant not breathing.
Firefighters took over lifesaving efforts from the family that had started CPR. The baby was taken to Beloit Memorial Hospital where the 3-month-old was pronounced dead.
Investigators say the 16-year-old mother had fed the baby around midnight. The two then went to sleep on a couch. The mother found her baby was unresponsive about four hours later and called 911.
An autopsy is planned.