Investigation into the disappearance of Karen Ristevski enters fifth month

Experts in the US have been called in as the search for Avondale Heights mum Karen Ristevski enters its fifth month.

She disappeared without a trace on June 29 2016.

The Herald Sun has revealed a key piece of evidence has been sent to the United States.

Investigators believe Mrs Ristevski probably met with foul play, but haven’t been able to find any clues despite extensive searches of the Maribyrnong River

Her phone pinged towers on the Calder Freeway on the day she disappeared, which has also prompted searches in areas northwest of Melbourne.

Police have again spoken with Karen’s husband Borce Ristevski as well as stepson Anthony Rickard but not in the sense of formal interviews.