Police dig up concrete in bid to solve cold case

Police investigating the cold case murder of an 18-year-old girl have failed to find anything of interest after excavating a Kawerau property this morning.

Mona Blades went missing on May 31, 1975, while hitchhiking from Hamilton to Hastings.

She got into an orange Datsun 120Y stationwagon on the Napier-Taupo road and disappeared without a trace. Her body and belongings have never been found.

Detective Inspector Mark Loper said the excavations at the Kawerau property were in response to new information received on the case last year.

It prompted police to undertake sonar work at the property, which uncovered "some areas" that warranted further investigation, he said.

Excavators drilled to a depth of about 80 centimetres, then probed a further 80 centimetres without finding anything of interest to the case.

A  Kawerau man has spent two decades trying to have the address checked by police and this morning, work started to try and lift a concrete floor in the laundry at the rear of the house.

"Files like this always remain open waiting for new information or a situation to change, and we regularly review 'cold cases' in a renewed effort to try and solve them," Mr Loper said.

"This work has not uncovered any item of interest and police and workers will shortly leave the property."

Mr Loper said the property under investigation in Kawerau was bought by its current owners last year.

They granted permission to carry out the excavations, he said.

He appealed for anyone with information about the historic homicide to come forward.

"Relationships and allegiances change over time, and sometimes people just want to get things off their chest."