Police call for assistance in search for missing Mount Barker woman

South Australia police are asking the public for any information about missing woman Rebecca Spiers, who went missing from Mount Barker three weeks ago.

Authorities are concerned for the welfare of the 38-year-woman as it is out of character for her not to contact her family.

Ms Spiers is Caucasian, 169cm tall, medium build, has straight blonde, shoulder-length hair and blue eyes.

Anyone who spots Ms Spiers or has information on her whereabouts is asked to contact the police assistance line immediately on 131 444 or Crime Stoppers on 1800 333 000.