A public tip-off has led Queensland police to a buried shipping container, as detectives investigate the 1974 murders of a mum and her two daughters.

A buried shipping container with a concealed hatch has been found during the excavation of a property in rural Queensland linked to a triple unsolved murder from 1974.

A tip-off from the public led police to the find near the Southern Downs town of Warwick.

The find comes a day after Thomas Edward Martin, 66, was released on bail on drug trafficking charges, following an earlier search which allegedly uncovered $300,000 in cash and 50kg of cannabis.

While police aren’t connecting him to the unsolved Brisbane murders, it is alleged that he is a close associate of a man suspected of being linked to the triple murders.

Properties near Warwick have been searched as detectives delve into the unsolved Brisbane murders of Barbara McCulkin, 34, and her daughters Vicki Maree, 13, and Barbara Leanne, 11.

They were last seen at their inner-city Highgate Hill home on January 16, 1974 and have never been found.

On Saturday, police found a buried container with a concealed hatch on a property at Massie, near Warwick, following a tip-off.

Search warrants were issued last week.

“As a result of fresh information received from the public we have returned to the property to inspect a suspicious site and located a buried shipping container,” Detective Inspector Mick Dowie said in a statement.

Police believe it may have been buried on the Willowvale Road property for several years.

Investigators have used breathing equipment to see if it had been used for drug trafficking.

Three men – aged 77, 75 and 52 – were last week released without charge after police found evidence of a large scale drug production ring at Yangan, near Warwick.