Two people acting suspiciously on a bridge in South Australia's mid north have led to the discovery of bullets and prompted a major search for a gun used in one of three murders linked to the Adelaide drug trade.
About 35 police personnel, including members of a special task force, converged on the Hutt River near Clare on Friday in the ongoing investigation into the suspected murder of Robert Atkins.
The 29-year-old went missing in November 2020 and is thought to have been killed and his body disposed of somewhere near Orroroo, 275 kilometres north of Adelaide.
Detective Superintendent Des Bray said the couple were spotted on the bridge by a truck driver late last month.
"It appears they became spooked on seeing the truck and left the area immediately and then returned a few minutes when they thought there was nobody left to see them," Supt Bray said.
"We know they got out of a vehicle and disposed of what we believe to be ammunition and also a firearm which we suspect may have been used in the murder of Robert."
Since then police have recovered more than 100 bullets and ammunition packaging and hope to be able to recover DNA and fingerprints from the material.
Their ongoing search will concentrate on the river, with divers covering an extensive area by hand, and also an area of roadway between Clare and Spalding.
Supt Bray said detectives were confident they knew the identity of the couple and expected to interview them soon.
He said police believed they were disposing of evidence on behalf of a murder suspect.
The murder of Mr Atkins is thought to have links to two other killings, those of Trevor King and Jeff Mundy.
Mr King, 41, was found dead at suburban West Lakes in January 2020 with police now believing his death was staged to look like a suicide.
Mr Mundy, 36, was last seen in December 2020. His body has not been found, with police suspecting it was disposed of somewhere on SA's Fleurieu Peninsula.
Up to 15 people are believed to have been involved in the murders and detectives are also checking another 200 drug overdose deaths since 2019 to determine if any more are suspicious.
In other inquiries into the death of Mr Atkins, Northern Territory police this week recovered an excavator and trailer, which police believe was stolen in SA in 2019 by those involved in his killing.
A 37-year-old man has been spoken to by police in relation to the excavator theft and is likely to be charged.