DENVER (KDVR) — The Denver Police Department said Monday morning that three people found dead in the Gateway neighborhood Sunday evening may have been caused by an overdose.

According to Denver Fire, crews were sent to the 4500 block of Kittredge Street as a medical response and tried to figure out what happened. Hazmat was dispatched as well but when the scene was cleared, all Denver Fire personnel left and DPD took over the incident.

Police said they’re investigating the triple deaths and that the office of the medical examiner will provide the victims’ IDs and cause of death.

This story was updated on Oct. 31 with DPD’s announcement that the cause of death is possibly due to overdose.