A number of reported CCTV 'blindspots' have been identified as detectives continue to probe Nicola Bulley's disappearance.
The mum-of-two vanished while walking her dog by the river in St Michael's on Wyre, Lancashire, at around 9.10am on January 27.
Her phone was found on a bench by the waterside and had recently connected to a work call, while her dog Willow was running loose.
Police have launched an extensive search of the area in the days afterwards, with "main working hypothesis" being that she fell in a river.
But Lancashire Police this week admitted some "blackspots" may have affected its investigation after no body was found, saying it is a remote "possibility" she left the area via the only path not covered by cameras.
It comes as new details suggested three crucial areas around the river were not under CCTV surveillance at the time of her disappearance.
The most crucial of these is around a footpath that leads from the river to Garstang Road and into the village.
Police have appealed to 700 drivers passing by the location on the day for "every piece" of dashcam footage that "helps us build up a picture of movements on that morning."
A second blind spot is said to be focussed on a path going from Wyreside Farm Caravan Park adjacent to the river to the nearby A586.
One of Nicola's friends, named Tilly Ann, has also claimed a third CCTV camera focused on another exit from the river was not functional at the time.
"The only camera that isn't working is the one that would have seen everything", she said.
Multiple diving team searches of the river by police and outside specialists have turned up no results.
Superintendent Sally Riley of Lancashire Police has repeatedly ruled out criminal or third-party involvement, and on Thursday reiterated the police’s belief that Nicola had fallen into the river.
“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.
The North West Police Underwater Search & Marine Unit were meanwhile spotted searching the sea at Morecambe Bay yesterday, close to where the River Wyre meets the coast.
Officers have reportedly confirmed they are now concentrating on the mouth of the river and believe that finding Ms Bulley in the sea after moving downstream has become "more of a possibility".
