Detectives have raided a third property as part of a 40-year-old triple murder investigation in Queensland.
Barbara McCulkin, 34, and her daughters Vicki, 13, and Leanne, 11, disappeared from their home in the inner-Brisbane suburb of Highgate Hill on the night of January 16, 1974.
Mrs McCulkin and her daughters have not been heard from since they went missing. Their bodies were never found and police believe they were murdered.
Police uncovered potential new evidence on Tuesday when they raided two properties near Warwick on the Southern Downs apparently linked to a person of interest in the case.
The raids, which detectives say uncovered new evidence in relation to the murders, led investigators to another farm in the area on Wednesday where they allegedly found $300,000 in cash as well as barrels of cannabis and a caravan also containing the drug.
The 66-year-old property owner was arrested, in what is the latest development in the cold case, which detectives believe could be linked to the infamous Whiskey Au Go Go nightclub fire in Brisbane in 1973.
The man has since been charged with drug offences and will appear in the Toowoomba Magistrates Court today.
Cold case investigators aided by regional detectives and Crime and Corruption Commission investigators have been examining the murders for most of this year.
Investigative journalist Matthew Condon explored the McCulkin murders in his book Jacks and Jokers, which details the extent of official corruption in Queensland through the 1970s and early 1980s.
In the book, he quoted witnesses who suggested Mrs McCulkin was murdered because she ready to publicly name her estranged husband, Billy McCulkin, over his supposed involvement in the nightclub fire.
Fifteen people died in the fire in what was at the time Australia's largest mass murder.
James Finch and John Andrew Stuart were convicted of the crime.Solving the murders could 'turn history on its heard'
Speaking on ABC Local Radio, Mr Condon said the latest police investigation should be "loudly applauded".
"Clearly they [police] have not taken this case lightly, they have vigorously reinvestigated this murder," he said.
"I spoke to individuals who were in Boggo Road [jail] in the late '70s and the murder was discussed.
"There were rumours and allegations that the two young girls had been sexually assaulted - there was even a rumour that those young women had been beheaded before their mother's eyes.
"There were rumours of police involvement, that corrupt police played a part in their disappearance.
"All these things have swirled around quite literally for decades.
"Which is why it is so astonishing ... to learn from the police that they have raided properties outside Warwick.
"If we get to the truth courtesy of this investigation it will turn history on its head in this state, there is no question about that.
"It might have happened 40 years ago ... the community needs to know that authorities are trying to heal a wound of that magnitude for us."
On Tuesday, Detective Steve Holahan said police were confident of solving the case.