Missing mum Nicola Bulley may have fallen into a river while trying to retrieve her dog's ball before getting weighed down by her clothes, police say.
The 45-year-old had dropped her two young daughters at school in St Michaels on Wyre last Friday morning before taking springer spaniel Willow out onto a nearby towpath.
The dog was later found running around alone, with her harness and lead on the floor, while Nicola's phone was on a bench still connected to a work conference call.
Police have spent the last eight days scouring the area, including the river - but are yet to find any conclusive evidence as to what happened.
However, they do not believe the disappearance is suspicious at this stage.
Have you been affected by this story? Let us know at webnews@mirror.co.uk
Today, Lancashire Police revealed their main line of hypothesis is that Nicola accidentally fell into the water - suggesting something may have happened with her dog.
Willow was not wet when she was found by fellow dog walkers but Superintendent Sally Riley told a press briefing it was "possible" Nicola toppled into the river while trying to retrieve a tennis ball.
The mum-of-two, who works as a mortgage adviser, was a avid walker and used tracking app Strava.
In a couple of photos posted on the app Willow can be seen carrying a ball.
Superintendent Riley told the MailOnline after the press conference: "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."
She said Nicola was wearing a quilted, ankle-length gilet, and underneath that another coat, as well as further clothing.
The officer also said Nicola had on ankle length wellington boots.
"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," she added.
During the briefing, Supt Riley said: "At the point where the bench is located there is quite a steep drop to the river, albeit not high, it is steep.
"And therefore whilst I don’t want to speculate as to what may have happened, it is our working hypothesis that she has entered the water accidentally and that’s why there is no physical evidence on the field."
She confirmed the mum can swim, and said due to the different water depths searchers have been both wading in the River Wyre and diving underwater.
The superintendent said after a "thorough" search of the immediate stretch of water, investigators have not found any conclusive evidence.
She went on to say: "The dog was off the lead, this was normal for the dog to run about and Nicola was on a teams call, which again it would be normal for her not to participate in actively and just have the phone to listen in, effectively.
"Anything could have happened with the dog whereby Nicola may have gone - and I don’t wish to speculate, we don’t know - but it is possible the dog was loose and off the lead that there may have been an issue with the dog that led her to go near to the water’s edge.
"She puts the phone down momentarily and Nicola may have fallen in. That is a possibility," said Supt Riley.
She confirmed the dog was dry when found by other walkers.
"We don’t believe the dog was in the river because the dog, we believe, was dry and the witnesses have not described the dog swimming or jumping into the river.
"We don’t know why Nicola may have entered the water if she did," she added.
