The 47-year-old has not been seen since she left the family home about 10am on June 29, after an argument with her husband. Mobile phone data shows the couple’s phones were both detected by transmitter towers on Melbourne’s Calder Highway that day, the Herald Sun reported on Saturday.

Mrs Ristevski’s mobile phone was reportedly tracked near Gisborne, 40km northwest of the family home in Avondale Heights, while her husband’s was tracked on the same highway, at Diggers Rest, about 20km northwest of the home.

It was also reported that Mr Ristevski’s phone was switched off for about two hours that day.

When quizzed by detectives on his whereabouts the day his wife disappeared, the missing woman’s husband said he had forgotten to mention he had driven Mrs Ristevski’s car that day.

He reportedly told police the fuel gauge of Karen’s 2004 Mercedes-Benz coupe was playing up so he wanted to test it out on the Calder.

Mr Ristevski claimed the fault corrected itself when he hit a bump on the highway, so he then returned home, the Herald Sun reported.

Police on Thursday focussed their search for the missing mother to rural areas northwest of Melbourne. Residents were asked to check for “any changes or any suspicious activity” since the woman’s disappearance.

The search has focussed on a former Ristevski family holiday spot at Barmah National Park in the State’s north multiple times, with police now turning their attention to the park’s bushland.

“Police have searched a number of locations across Victoria however their focus remains in the rural area to the northwest of Melbourne,” a police spokeswoman said in a statement on Thursday.

The appeal for help followed media reports on Wednesday that police were searching the Murray River at Barmah.

The Maribyrnong River, west of Melbourne has also been searched on at least two occasions since Ms Ristevski’s June disappearance.