Seven News tonight revealed a bombshell breakthrough in the case of the missing Beaumont children, 52 years after the three siblings disappeared from a beach in Adelaide, disclosing a new dig site at North Plympton near where Jane, 9, Arnna, 7, and Grant, 4, went missing at Glenelg beach in 1966.

Police first dug at the site in 2013 after details were published in a book titled The Satin Man, in which a man claimed his father, who turned out to be local businessman Harry Phipps, had killed the children.

Phipps was not named in the book but it gave enough information for people to identify him.

A group of young men also came out and said Mr Phipps, who died in 2004, asked them to dig a trench at his manufacturing business’ factory, Castalloy.

Police dug it up in 2013 but found nothing.

But a Seven News investigation has revealed an anomaly was discovered in another spot at the site — an area of disturbed earth — just two weeks ago, through the use of a ground penetrating radar.

As of Monday night, the factory is a crime scene.

Detectives from the Major Crime Investigation branch will conduct a new excavation of the property in coming weeks.

The Beaumont children disappearance case sparked one of the largest police investigations in the country’s history.

Clues as to what happened to the siblings have continued to surface since their disappearance from Glenelg Beach on Australia Day 1966, but leads have always led to dead ends.

Sightings of the children at Glenelg on the day they disappeared put them in the company of a tall, blond and thin-faced man with a suntan.

In late 2016, South Australian Police identified a 71-year-old former Adelaide scout leader as a person of interest in the mystery.

Millionaire bar owner and convicted paedophile Anthony Munro is in jail for unrelated child sex offences in South Australia dating back to 1962 — four years before the Beaumonts vanished.

Police interviewed Munro in June 2016 about Australia’s greatest child abduction mystery after a child’s diary said he was at Glenelg beach in the days surrounding the Beaumont children’s disappearance.

The “salvage and exploration club” diary was kept by one boy, and contributed to by another, tracking their adventures diving off the Adelaide coast that summer.

Police have previously said there is no evidence linking Munro to the disappearance of the Beaumont children.

Another man who was linked to their deaths, Munro’s friend Allan “Max” McIntyre, died in a nursing home on the Yorke Peninsula west of Adelaide June last year, aged in his late 80s.

His son, Andrew McIntyre, who was sexually abused by Munro, broke his silence last year revealing his father and Munro were frequenting Glenelg beach in the days around the disappearance of the three children.

Highly regarded detective Stanley Swaine, who died in 2002, was widely discredited following his retirement from the South Australian police force, but his obsession with the case continued well into his second career as a private investigator.

Mr Swaine wlead the case from 1967 when the Beaumont parents believed their children could still be alive.

He notoriously made an abortive trip with Jim Beaumont to Melbourne to investigate letters written by a person who claimed to know where the children were and that they were well-looked after.

In 1996, after the 30th anniversary of the children’s disappearance, Mr Swaine made the outrageous claim that he had found a 40-year-old Canberra woman who was Jane Beaumont.

He said all three Beaumont children had been taken and raised by a satanic cult.

Weeks before he died, Mr Swaine made another claim about the Beaumont children to a journalist, saying he knew where they were buried and that a priest had told him it was in a church cemetery in Adelaide.