Detectives believe Nicola Bulley may have fallen into a river trying to pick up a tennis ball for her dog and became weighed down by her heavy winter clothes.
The mother-of-two, 45, went missing a week ago leaving her family distraught as a police hunt continues.
She was last seen wearing an ankle-length black quilted gilet jacket, a black Engelbert Strauss waist-length coat, tight-fitting jeans and green wellies.
She had a pale blue Fitbit strapped to her wrist as she took her Spaniel, Willow, on a walk through River Wyre - a route she took often after dropping her two daughters to school nearby.
Police revealed they suspect Ms Bulley likely fell into the 15ft-deep river last Friday morning.
Ms Bulley posted images of herself exercising along the same stretch of the River Wyre to where she was last seen last on the running tracking app Strava.
In two of the photos Willow is seen playing with a ball.
Superintendent Sally Riley said police did not believe that anyone else had been involved in her disappearance and that she fell.
She added: “I’m not aware of a dog ball being retrieved but it’s possible that a ball could have rolled down the steep bank close to the edge of the water and Ms Bulley was bending down to pick it up.
“What she was wearing could also be a factor.
“I don’t wish to speculate but the facts are that she was wearing a quilted, ankle-length gilet, which is a big coat, and underneath that there was another coat and then under that coat more clothing.
“She was also wearing ankle-length wellingtons. One would assume they fill with water when someone enters a river so all of that clothing is heavy, particularly on someone who is of slight build and only 5 foot three.”
Ms Bulley, 45, was last seen next to the river in St Michael’s on Wyre, Lancashire, one week ago.
Superintendent Riley told a press conference on Friday that police were working on hypothesis that Ms Bulley had fallen into the river.
She said police firmly believed that that missing mother did not leave the riverside, and that she vanished during a 10 minute window.
Supt Riley said: “This is not suspicious but a tragic case of a missing person.”
The officer said police were sure Ms Bulley had not left the area where she was walking the dog adding: “Several of the exits are either locked or covered by CCTV we have been able to negate that Nicola left ... we are as sure as we can be that Nicola did not leave the area.
“At the point at where the bench is located the bank is steep it’s our working hypothesis that she entered the water accidentally ...”
Earlier on Friday, Ms Bulley’s partner Paul Ansell said it was as though “she has vanished into thin air”.
Ms Bulley, from the village of Inskip in Lancashire, vanished after dropping off her daughters, aged six and nine, at school.
In his first TV interview, her partner of 12 years, Paul Ansell, said the family was “going round and round and round” through every possible scenario, while describing the last week as “like a dream”.
“I just can’t believe that we’re a week on and as yet it seems like we’re no further - it just seems absolutely impossible, like a dream,” the engineer told Sky News on Friday, as he joined friends retracing her steps.
“I cannot get my head around any of it. Every single scenario comes to a brick wall.
“All we’re doing is sitting there going round and round and round, going through every scenario and then go back to the first scene again and do the whole thing again...it’s just all day long.
“My whole focus is the two girls. Just staying as strong as I can for them.”
He added that huge search efforts made by the local community have brought the family “a great amount of comfort”.
“We don’t have anything else do we? We’re never ever going to lose the hope - of course we’re not,” he added.
“But right now it is as though she has vanished into thin air. [It’s] just insane.”
A wide-scale search for Ms Bulley on Friday entered its eighth day as divers continued scouring the river, and a local resident told how women are in fear of going out alone.
On Friday, police cordoned off a car park and footpath nine miles downstream from where Ms Bulley disappeared.
Officers taped off Skippool Creek car park in Poulton-le-Fylde, Lancashire, while forensic analysis took place.
The car park has since been reopened.
Following a police appeal, officers on Thursday identified a woman in a red coat who had been pictured walking in the area around the time Ms Bulley disappeared, and who detectives hoped may have been a key witness.
But investigators and Ms Bulley’s loved ones have been dealt a blow as it emerged the woman - 67-year-old Christine Bowman - had not seen anything significant.
The retired teacher told the Daily Mirror on Friday she had already spoken to officers and “doesn’t know anything”.
“It has made local women fearful,” she added. “If they have husbands or partners, they have been taking the dogs out instead.”
Timeline of events
January 27
Ms Bulley dropped her daughters – aged six and nine – off at school in the morning before walking her dog, Willow, in St Michael’s on Wyre, Lancashire.
Lancashire Police have said she had been walking along a path beside the River Wyre just before 9am.
She was seen by a dog walker who knew her at around 8.50am, and their pets interacted briefly before they parted ways, according to the force.
At 8.53am, Ms Bulley sent an email to her boss, before logging on to a Microsoft Teams call at 9.01am.
She was seen by a second witness at 9.10am – the last known sighting.
By 9.30am, Ms Bulley’s Teams call had ended, but her phone stayed connected to the call.
Approximately five minutes later, another dog walker found her phone on a bench beside the river, with Willow darting between the two.
At 10.50am, Ms Bulley’s family and the school attended by her children were told about her disappearance.
Lancashire Constabulary launched an investigation into Ms Bulley’s whereabouts on the same day and appealed for witnesses to contact them.
January 28
Lancashire Constabulary deployed drones, helicopters and police search dogs as part of the major missing person operation.
They were assisted by Lancashire Fire and Rescue Service, as well as Bowland Pennine Mountain Rescue team and the North West Underwater Search Team.
January 29
Local residents held a meeting at the village hall to organise a search for Ms Bulley at 10.30am on Sunday and around 100 people joined the search.
Police urged volunteers to exercise caution, describing the river and its banks as “extremely dangerous” and saying that activity in these areas presented “a genuine risk to the public”.
January 30
Superintendent Sally Riley from Lancashire Constabulary said police were “keeping a really open mind about what could have happened”, and that they were not treating Ms Bulley’s disappearance as suspicious.
January 31
Lancashire Constabulary spoke with a potential witness – a man who had been walking a small white fluffy dog near the River Wyre at the time of Ms Bulley’s disappearance.
Her family released a statement saying they had been “overwhelmed by the support” in their community, and that her daughters were “desperate to have their mummy back home safe”.
February 1
Ms Bulley’s parents, Ernest and Dot Bulley, spoke to The Mirror about the “horror” they faced over the possibility of never seeing her again.
Her father told the newspaper: “We just dread to think we will never see her again, if the worst came to the worst and she was never found, how will we deal with that for the rest of our lives.”
February 2
Lancashire Constabulary spoke with a second witness who they had identified with the help of the public using CCTV – but they told police they did not have any further information to aid their inquiry.
Officers from the North West Police Underwater and Marine support unit searched the area close to where Ms Bulley’s mobile phone was found, while police divers scoured the River Wyre.
Meanwhile, Ms Bulley’s family appealed to the public for help tracing her.
Speaking with Sky News, her sister Louise Cunningham said: “There has got to be somebody who knows something and all we are asking is, no matter how small or big, if there is anything you remember that doesn’t seem right, then please reach out to the police.
“Get in touch and get my sister back.”
Ms Bulley’s father said his family hoped their interview would “spark a light” that would lead to her being found.
February 3
Lancashire Police said they were working on the hypothesis that Ms Bulley may have fallen into the River Wyre.
Superintendent Sally Riley urged against speculation, but said it was “possible” that an “issue” with Ms Bulley’s dog may have led her to the water’s edge.
She urged the public to look out for items of clothing Ms Bulley was last seen wearing, and gave an extensive list.
Ms Bulley’s friends also shared heartfelt appeals via television interviews, including Emma White, who told the BBC that Ms Bulley’s daughters were continually asking where she was.
