Police say they believe Nicola Bulley “sadly” fell into a river as they focus on a 10-minute window from 9.10am to 9.20am when the dog walker went missing last Friday.
Officers said she has not been found despite an extensive search of the area, along the River Wyre and 15km to the sea.
Police said an unprecedented amount of resources had gone into the search for Ms Bulley.
The 45-year-old was last seen on 27 January at about 9.10am on a path by the River Wyre in the Lancashire village of St Michael’s on Wyre.
Her phone was found on a bench still connected to a work call, while her springer spaniel dog was running loose.