A health worker missing in remote South Australia is thought to have been abducted from her outback home, prompting a wide-scale air and land search.
It's believed Gayle Woodford, 56, was taken from outside her home in Fregon, on the APY Lands, early on Thursday morning.
A four-wheel-drive ambulance that she used in her work has been recovered and is being forensically examined.
One of three people using the vehicle when it was located in Coober Pedy on Thursday has been arrested and charged with theft.
Ms Woodford's disappearance has also been declared a major crime.
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"We've got grave fears for the safety of Gayle, very grave fears, and, at this stage, we are hoping for the best and we are doing everything we possibly can in case she is out there somewhere injured," Superintendent Des Bray told reporters on Friday.
Ms Woodford was last seen on Wednesday night and was reported missing on Thursday when she failed to report for work at the local health clinic.
A GPS device in her ambulance shows it left Fregon early on Thursday and travelled to Mimili.
It then travelled to Indulkana, Marla and finally onto Coober Pedy where it was intercepted by police.
The 36-year-old man behind the wheel has been remanded in custody on the theft and driving charges while no charges were laid against a second man and a woman.
Police have called for anyone who spotted the ambulance travelling between Fregon and Coober Pedy to come forward.
They have a report of a possible sighting of Ms Woodford at Marla at about 6am on Thursday but are yet to confirm it if was the missing woman.
Supt Bray said the most likely scenario was that, for some reason, Ms Woodford left the safety of her own house and something happened to her outside.
