MAJOR Crime detectives have named a deceased man as a person of interest in one of South Australia's most notorious cold case as they prepare for a new dig site.
Police will excavate a six square metre area hole at the business premises of New Castalloy at North Plympton within the next fortnight in the search for the Beaumont children, who went missing from Glenelg on January 26, 1966.
Detective Superintendent Des Bray said they are reviewing inquiries made about Harry Phipps - chairman and co-founder of Castalloy and a principal suspect in the disappearance - who died in 2004.
Investigators first looked into Mr Phipps in 2007 and in 2013 excavated a site at the Mooringe Ave factory after two men had claimed they dug a three-metre deep hole under the businessman's request in the days after Jane, 9, her sister, Arnna, 7, and brother Grant, 4, went missing.
Det Supt Bray said the claims by both men were "helpful, cooperative and truthful".
"It's never been in doubt they dug a hole, it's about where the hole was dug," he said.
"But they were boys and it was 50-odd years ago ... and for a number of reasons they believed it (the hole) could be further along (from the first excavation site).
"There's never anything to prove that the Beaumont children are in the hole, however, common sense says that if there is a slightest chance that this hole could be relevant, we should search and that's what we're doing."
On January 4-7, Flinders University conducted what was known as Electrical Resistivity Tomography testing, which involved placing a number of probes into a defined area and using electricity to analyse what's underneath.
Police will conduct another dig about 50m away from the previous excavation after a small anomaly was found in the ground.
"There is a need to temper expectations. We don't know what we would find," Det Supt Bray said.
"There could be an innocent explanation ... it certainly wasn't suggesting it was a grave, but certainly it was sufficient to warrant further investigation and that's what we've committed to do."
Det Supt Bray said police have yet to prove Mr Phipps either committed the crime or conclusively rule him out alongside dozens of other people of interest.
But a "discreet" investigation into Mr Phipps was relaunched in 2017.
"The reason for that was to try to minimise the negative impact on the family," Det Supt Bray said.
"Mr and Mrs Beaumont are both alive and whenever something comes up we try to do it in a way that causes the least distress for them possible."
He stressed that Mr Phipps was not a suspect.
Police have undertaken many actions and lines of inquiry in relation to this matter which they have not - and will not - detail in the public environment as per ongoing criminal investigation.
Det Supt Bray refused to comment on claims from Mr Phipps' son that he saw the Beaumont children at the family home, which prompted the 2013 excavation.
He said police will not be making further comment with regard to the active investigation at this time before the excavation begin.
Anyone with fresh information in connection with this matter to call Crime Stoppers on 1800 333 000 or report online at www.crimestopperssa.com.au
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