The death of an infant is being ruled a homicide, and police are questioning a relative.

Oak Lawn police are questioning a family member and conducting a homicide investigation after a 5-month old-girl died Sunday in the southwest suburb, officials said.

Officers were called at about 10:46 a.m. to a home on the 6600 block of 91st Street for a report of an "armed subject," said Oak Lawn Police Chief Michael Murray. While responding, officers were informed that the infant had "suffered a significant injury," police said.

Murray said the child was less than a year old, but offered few other details at a Sunday evening news conference. He declined to specify the baby's gender or discuss the nature of its injuries. Murray also declined to say whether the child lived at the home where she was found.

Police immediately began life support measures after arriving at the home, Murray said. Oak Lawn Fire Department paramedics were called and took the child to Advocate Christ Medical Center, where she was pronounced dead at 1:48 p.m., police said.

Cook County medical examiner's officials said the child was a 5-month-old girl.

An investigation determined that the parents of the child left the baby with a relative and were not at the home at the time of the incident, police said.

Relatives of the child told police that a family member was involved in the incident. The family member was being questioned by Oak Lawn police Sunday evening. No charges had been filed.

Cook County prosecutors along with the Oak Lawn police department and south suburban major crimes task force are investigating.

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