Police said later on Thursday that: "indications from the initial stages of the investigation show it would have been extremely unlikely for the driver of the vehicle involved not to know a collision had occurred".
Fay's body was discovered near the intersection of Anzac Parade and Helmore St at about 1.55am on Wednesday.
She had suffered injuries consistent with a vehicle collision, but police who searched the area had been unable to locate a vehicle.
Detective Sergeant Craig Gorringe urged the person or people involved to do the right thing and come forward about what had happened.
"We are also seeking any CCTV footage from overnight from businesses or residences on Anzac Parade, along with any sightings of the elderly woman in the Anzac Parade area prior to the time her body was found," he said.
Anybody with information could contact police on 105 or Crimestoppers anonymously on 0800 555 111.