Emergency services were called after reports were received for the welfare of a woman in the river at Kirkby Lonsdale.
Police were called last night at about 7.25pm to Devil's Bridge, Kirkby Lonsdale.
The woman was last seen in the water and described as in her 50s and wearing a red puffa jacket and jeans.
Officers are appealing for anyone who was in the area at the time or who might have seen a woman fitting this description in the area.
Searches were being carried out in the area with officers assisted by Cumbria Fire and Rescue, Swift Water Rescue and National Police Air Service.
Anyone with any information is asked to contact police on 101 quoting log 194 of May 22.
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