Authorities hold serious concerns for a German backpacker who is believed to be missing in Western Australia's Wheatbelt region. 

Carolina Wilga, 26, has been backpacking through Australia for the past two years and works on mines to fund her stay at hostels.

She was last captured on CCTV in the Beacon area on June 29 — the same day she was last in contact with her friends.

Police believe she visited a convenience store on Stirling Terrace in Toodyay the day before.

Her family, with whom she keeps in regular communication, are worried as they have not heard from her since June 18. 

"We are very concerned for her welfare," WA Police Commissioner Col Blanch said today.

Police have been conducting large-scale land and air searches for Wilga. 

The homicide squad have now joined the investigation.

Blanch stressed that her disappearance is not being treated as a murder "at this point" and their involvement was to have "our very best capabilities to investigate something that is very concerning to us".

Searches are continuing, and anyone with any information is urged to contact police.

Police are also appealing to anyone with footage of the Beacon area and the surrounding north-east Wheatbelt area between June 29 and July 4 to come forward.

Wilga is described as having a slim build, with frizzy or curly long dark blonde hair, brown eyes and several tattoos, including one which depicts symbols on her left arm.

She may also be driving a black and silver 1995 Mitsubishi Station sedan with Western Australian registration 1HDS 330.

"What we would ask is our community keep their eyes and ears peeled for anything relating to the whereabouts of Caroline," Blanch said.

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