A Queensland man, 75, considered by police as a person of interest in a cold case triple murder, has denied any involvement.

A 75-year-old Queensland man who was detained by police on Saturday, denies involvement in an unsolved triple murder 40 years ago.

Vincent O’Dempsey and two other men, 77 and 52, were detained after police allegedly found evidence of large scale drug production at a rural property on the Southern Downs near Yangan, southwest of Brisbane.

All three were released without charge on Saturday night.

Mr O’Dempsey is considered by police as a person of interest in the murders of Barbara McCulkin, 34, and her daughters Vicki Maree, 13, and Barbara Leanne, 11, who vanished in 1974.

Mr O’Dempsey and Gary Dubois were charged with the murders in 1980, but the allegations were dropped the following year due to insufficient evidence.

Last week, police sensationally announced they had seized new evidence in the cold case after searching two rural properties on the Southern Downs in Warwick.

Police charged a 66-year-old associate of Mr O’Dempsey’s with drug trafficking after allegedly finding a large amount of cannabis and cash at a third property in the area.

On Sunday, Mr O’Dempsey’s lawyer Terry O’Gorman said his client “strongly denies any involvement whatsoever” in the disappearance and murder of the McCulkins.

He called on senior police to stop manipulating the media by released damaging information that had little credibility.

“He was the subject of a detailed committal hearing 30-plus years ago,” Mr O’Gorman told AAP of his client.

“The DPP (Director of Public Prosecutions) then decided there was insufficient evidence to justify a continued prosecution.

“He is a fellow who’s 75, in middling health, and he should not be subject to this constant barrage of `facts’ that are essentially the subject of smoke and mirror tricks.”

Some believe the McCulkins were killed because they knew too much about the 1973 Whiskey Au Go Go nightclub arson that killed 15 people.

They were last seen at their home in the inner Brisbane suburb of Highgate Hill on January 16, 1974.