A search operation to find Nicola Bulley has now moved to Morecambe Bay with police seen combing the area.
Nearly two weeks on from her disappearance, two boats with specialist police teams have been seen in the sea.
They were then spotted moving upstream searching either side of the River Wyre.
The 45-year-old went missing while walking her dog in St Michael's on Wyre, Lancashire, on 27 January.
Officers have reportedly confirmed they are now concentrating on the mouth of the river and believe that finding Ms Bulley "in the open sea becomes more of a possibility".
A Lancashire Police statement read: "Our investigation to the disappearance of Nicola Bulley is continuing and we continue to search areas of the River Wyre and surrounding area.
"People may have seen less police activity today than previously in the area of the river above the weir but that is not because we have stepped down our searches, it is because the focus of the search has moved further downstream into the area of the river which becomes tidal and then out towards the sea."
It comes after a dive search specialist with years of experience claimed the missing mum-of-two was not in the river.
Peter Faulding's independent Specialist Group International (SGI) firm were drafted in earlier this week to aid Lancashire Police divers with their high-tech sonar equipment.
But he has now told the Mirror they have completed scouring the area of river from where Nicola's phone was found - and where investigators theorise she likely fell in on January 27.
"We’ve done our job and we’ve cleared the areas that we were tasked with by Lancashire Police and we are happy that there is nothing in that water," he said.
But during a press conference in St Michael's on Wyre village hall, superintendent Sally Riley of the Lancashire Constabulary, said that while Ms Bulley has not been found, it does not necessarily mean she wasn't in the water.
"Our search has not found Nicola in the river and then a re-search in parts by SGI has found the same," she said.
But Superintendent Riley said that the police still believes that Ms Bulley could have fallen into the water.
“In the light of other inquiries being discounted from the investigation so far… clearly our main belief is that Nicola did fall into the river," she said.
“Clearly Mr Faulding isn’t included within all the investigation detail any more than the members of the public are that I’m briefing through these sorts of press conferences.”
Ms Bulley vanished on January 27 after dropping off her two children at school in St Michael's, Lancashire, before taking family dog Willow for a walk on a nearby trail.
However, her phone was later found on a bench, with the springer spaniel wandering nearby without her harness.
Superintendent Riley has also urged the public this week to avoid "distressing" speculation about what might have happened to Ms Bulley.
"We would ask that people in the wider community, particularly on social media and online, do not speculate as to what may have happened to Nicola," she said
