A person of interest in a 40-year-old cold case murder investigation has been arrested with two other men on a property near Yangan in South East 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 say during a search of a property in the Southern Downs Region on Saturday morning they allegedly discovered evidence of an illegal drug operation.

Three men have been taken to the Warwick police station for questioning.

Police uncovered potential new evidence in the case on Tuesday,when they raided two properties near Warwick, 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 was another development in the cold case, which detectives believe could be linked to the infamous Whiskey Au Go Go nightclub fire in Brisbane in 1973.

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 was 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.