A Toronto mother has been charged with aggravated assault after her injured toddler died in hospital.

Police were called to a home in the city's northwest end, near Jane Street and Lawrence Avenue, early Wednesday morning for a medical emergency.

Officers located an 18-month-old boy suffering from "obvious signs of trauma."

The baby was taken to hospital, where he later died of his injuries.

Police wouldn't elaborate on the specific injuries the toddler sustained.

Melissa Alexander, 22, has been charged. She is to appear in court on Tuesday.