The staff were not physically injured.
The suspect is described as in his 30s with a dark complexion, 180cm tall, medium build with dark brown hair. He was wearing a long sleeved hooded top with a red chequered pattern, according to SA Police.
Anyone who spots a man matching the description in the area is asked to contact police on 131 444.
If you have any information that may assist the investigation, contact Crime Stoppers on 1800 333 000.
