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The 36-year-old was last seen on the riverbank, west of the Balclutha bridge, about 3pm on Monday.
Senior Sergeant Richard Whitmore, of Balclutha, said 20 Search and Rescue personnel searched the river bank and the river using four boats loaned by the Balclutha Jet Boating Club.
The ground search and river search using jet-boats would continue today.
A private helicopter was also used in the search, which covered an area from the Stirling Bridge to where items belonging to Miss Carson were found, about 200m west of the Balclutha bridge.
A friend of Miss Carson raised the alarm late on Tuesday.
"Miss Carson appears to have been in a distressed state when she was last seen and we do hold grave concerns for her safety," Snr Sgt Whitmore said.
An inquiry team of eight police staff was also working to gather information about Miss Carson's activities over the past few days.
She is described as Caucasian, of medium build, 169cm in height, with long dark hair. She was last seen wearing a black fleece top, blue jeans and blue plastic shoes.
Anyone who saw her on the riverbank on Monday afternoon is asked to contact Balclutha police on (03) 418-0203.