The death of a 3-month-old infant in an unincorporated area near Des Plaines remains under investigation, a spokeswoman from the Cook County Sheriff's Department said Sunday.
The matter has been classified as a suspicious death.
The investigation began about 1:55 p.m. Thursday when Glenview police and North Maine Fire Protection District firefighters responded to the 10100 block of Holly Lane after receiving a report that the boy was not breathing.
North Maine fire personnel took the boy to Advocate Lutheran General Hospital in Park Ridge, where he was pronounced dead.
Cook County sheriff's officials were notified after it was determined that the death occurred in an unincorporated area near Des Plaines.
According to the sheriff's department, the victim's father found the infant unresponsive on a mattress placed on the floor, about 15 minutes after he put the child down for a nap.
Investigators interviewed the boy's mother, who was at work at the time, and the father. There was no obvious sign of trauma, according to the sheriff's department.
The Cook County Medical Examiner's Office said Sunday an autopsy was complete, but the results are unavailable "pending further studies."