Police have found a car connected with a murder investigation after a two-day search of a Hells Angels property at Ponde.
A team from SA Police's major crime investigation branch had scoured the 15-hectare property on Kenny Road, the site of an annual sand drag racing event hosted by the outlaw motorcycle club.
Just as officers prepared to call an end to the search on Wednesday afternoon, they found a Toyota Echo they believed was used by three men who murdered Mark Boyce in 2017.
The car was buried deep beneath the sand and burnt out.
Police planned to remain at the scene overnight last night to continue their investigation.
Less than two hours earlier, Detective Superintendent Des Bray had despaired at officers' inability to track down the car, or pistols used to gun down Rebels Motorcycle Club members Graham Nixon, Sinibaldo Palombi and Hubert Western in 1999.
All they had found to that point was a shotgun and a rifle, ammunition, a number of stolen vehicles, and plastic tubing they believed had been used to store the murder weapons as they were buried beneath the sand.
"Both investigations linked to this week's search are challenging cases, but we have not given up hope of being able to resolve them over time," he said.
"We know that just one piece of accurate information at the right time can provide a breakthrough.
"We never close cases such as these, no matter how difficult."
Murray Mallee police, the state tactical response group, mounted officers and sniffer dogs had identified sites of interest across the property on Tuesday before officers used ground-penetrating radar, loaned from the Australian Federal Police's national anti-gangs squad, and an excavator to investigate further.
A tip-off had suggested the pistols and the car police had sought could be buried at the property.
"The people involved, that we're investigating, are extremely well versed in police methodology and how to avoid detection," Superintendent Bray had said on Tuesday.
The two guns police found were stashed in a building.
Officers spoke with, but did not arrest, a Hells Angels member who was present when they arrived on Tuesday morning.
The man initially ran from police when he saw them approaching, but was captured as he fled through the scrub.
"The reason for him fleeing is yet to be firmly established," Superintendent Bray said.
Mr Boyce died after being assaulted by three men on Hill Street, Elizabeth South.
One of the men has since been arrested and charged, but the other two remain at large.
Mr Nixon, Mr Palombi and Mr Western were members of the Rebels Motorcycle Club who were shot outside their clubrooms on Wright Street, in Adelaide's city centre.
Two Hells Angels were arrested over the deaths, but the charges were later withdrawn after members of the Rebels refused to cooperate with the investigation.