A 55-year-old woman who vanished from a bush birthday party at a
campsite north-east of Adelaide has left police "puzzled" as to why she wandered away.
Deborah Pilgrim was last seen at 6am on Sunday, after celebrating a 60th birthday at the property, which is located on the outskirts of the town of Sedan.
Emergency services have launched a large-scale search of the area including mounted police and SES volunteers who are scouring the dense bushland.
Ms Pilgrim is described as being Caucasian, of slim build, 163cm tall and weighing approximately 55 kilograms. (SAPOL)
Police, as well as volunteers from the SES are poised to launch a joint search operation this morning. (Nine)
Ms Pilgrim's partner, Harry, is among concerned family and friends who've been anxiously watching the search unfold.
SA Police superintendent James Blandford said it's a "puzzle" as to why Ms Pilgrim wandered away from the campsite, but the disappearance is not being treated as suspicious.
"She is simply a missing person," Superintendent Blandford said.
Mounted police joined the search yesterday for Ms Pilgrim. (Nine)
"It's very easy to roll an ankle (and) it's very easy to fall into a ditch and maybe break a limb.
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"There are also some venomous snakes out in the scrub, so we've got concern that she's ... lying somewhere waiting for assistance."
Ms Pilgrim is described as being Caucasian, slim build, 163cm tall and weighing approximately 55 kilograms. She was last seen wearing blue jeans and a black shirt.
South Australian Police have urged the public to help locate Ms Pilgrim, with sightings of her to be reported to local authorities on 131 444.