COLUMBUS (AP) — Columbus police have opened investigations into the May deaths of two toddlers who died of drug overdoses in separate incidents.

Franklin County Coroner Anahi Ortiz said an 11-month-old boy and a 14-month-old girl both died from acute intoxication of heroin mixed with fentanyl.

The Columbus Dispatch reports police are treating both deaths as unrelated.

In the case of the 11-month-old, officers responded to a call reporting that the baby was not breathing and had turned purple. The 14-month-old was traveling in a car when a call was placed saying that the girl was not breathing.

Ortiz says autopsies and toxicology tests could not determine whether the children died by accident or homicide.

Homicide Sgt. Christ Holzhauser says the coroner alerted police this week that the children’s deaths were drug-related.