Shortly before 8 p.m. Sunday, EMS workers responding to a 911 call rushed to an apartment on Westfield Avenue to find an unresponsive Dayanna Orozco, who was pronounced dead at the scene.
An autopsy by the Union County Medical Examiner's Office revealed Monday that the manner of death was homicide.
The victim's mother, Raquel Ramirez, 30, has been arrested and charged with third-degree aggravated assault in connection with injuries sustained by the young girl, with bail set at $50,000.
The investigation is continuing, and authorities say additional charges in the case are possible.
Anyone with information is asked to call Elizabeth Police Detective Raymond Smith at 908-558-2000, Ext. 2017.