Police arrested Deanna J. Joseph, 39, of Alloway Township, by New Jersey State Police after she called 911 Saturday night around 9:30 p.m. seeking medical aid for her daughter.
According to police, Joseph took heroin and then drove around Alloway Township with her 2-year-old in her car.
Police said Joseph parked the vehicle and then returned to find the child inside unresponsive who died from her injuries.
"It appeared the child was confined in a car seat for an extended period of time while the mother was under the influence of drugs, and may have injured herself in the car seat" authorities said.
Lenahan said there were no obvious signs of injury to the child. Authorities said they are still awaiting autopsy results which should determine how the little girl died.
Police said this is Joseph's third arrest in nine years on charges related to neglect of a child authorities said.