Police will excavate a grave in the Quorn cemetery on Thursday, expecting to find the body of a 16-year-old girl, one of two murder victims in the South Australian mid-north town.
Detective Superintendent Grant Moyle said the Port Pirie girl, named by police as Rebecca Elizabeth Wild, was known to have been buried in a shallow grave at the site.
A 19-year-old man has been charged with Ms Wild's murder and also with the murder of 22-year-old Quorn woman Jasinta-Leigh (Jessie) Fullerton who was found dead on a road in the town on Wednesday morning.
She had suffered extensive head injuries.
Det Supt Moyle said the man arrested was known to both victims, and police were confident only one person was involved in the two murders.
'It would appear the murder of Jessie was the result of her coming across this person with the first victim,' he said.
'As a result of that, it will be alleged that is why she was murdered when she was.'
Det Supt Moyle said describing Ms Fullerton as just being in the wrong place at the wrong time would be 'one way of putting it'.
The arrested man was scheduled to appear in the Port Augusta Court on Thursday charged with two counts of murder.
Police said he was a member of the local State Emergency Service (SES) brigade and, as a result, detectives would examine the local SES station and an SES vehicle.
Ms Wild was reported missing by her family on Tuesday.
The body of Ms Fullerton, a well-known outback identity who rode camels in bush races, was found early on Wednesday morning next to her ute, less than 100 metres from her home.
She was last seen leaving a local hotel just a few hours earlier.
Det Supt Moyle said the course of events that had unfolded in Quorn over the past 24 hours was unusual.
'I thought nothing much would surprise me after my time in major crime, but this certainly has,' he said.
'It's quite a tragic event.'