Police first dug at the site in 2013 after details of the theory were published in a book titled The Satin Man.
The book outlined a case against a man, later identified as deceased businessman Harry Phipps, who was referred to as the “Satin Man” due to his apparent fetish for wearing satin clothing.
One of the book’s authors, Alan Whiticker, said Phipps’ own son accused him of killing Jane, 9, Arnna, 7, and Grant, 411
“The (Satin man’s) son came forward to us and said he did see the Beaumont children the day they disappeared,” Mr Whiticker told 9NEWS in 2016.
“They came into the backyard of the family home, which is no more than 500 metres from where they were last seen.”
Two other potential witnesses have claimed they’d dug a hole for Mr Phipps at the factory, which he owned at the time.
When Police searched there unsuccessfully in 2013, they were questioned as to why they dug in one small area and were accused of ignoring information from the two men who claimed to have dug the hole.
“The men weren’t present when the police dug a very small section of the factory and we would have liked them to have done a little bit more extensive excavation and perhaps had these men on board to say what exactly happened 40 years ago,” Mr Whiticker said.
9NEWS understands that since that search, police have been provided with new information which supports claims that another area of the property needs to be explored before the theory can be either confirmed or laid to rest.
Mostyn Matters, a retired detective who worked on the case, has today told 9NEWS the theory needs to be fully investigated.
Police are yet to reveal when they will return to the factory.