Detectives searching for missing Gaynor Lord say they have not been able to establish her state of mind with “any degree of confidence”.

Norfolk Constabulary released new CCTV footage on Wednesday of what they believe is the last sighting of Ms Lord before she disappeared in Norwich on Friday.

Officers said “everything we know is pointing to a high probability” that she went into the River Wensum, saying “nobody knows why she’s done what she’s done.”

The 55-year-old mother-of-three disappeared after leaving work early from Norwich city centre at 2.45pm.

Her belongings were found in Wensum Park – around 1.5 miles away from her workplace at Jarrold department store – and her coat was discovered in the river, which runs through the park.

Chief Superintendent Dave Buckley said: “There’s nothing we’ve been able to establish that really gives us a clear position on her state of mind that I would feel any degree of confidence of saying what we think it is at the moment.”

He said: “We continue to talk to friends, family, anybody who can help us that we know she’s had contact with.

“We have got hold of her mobile device, we will work our way through that systematically … and see if we can find out more accurately why we’ve ended up where we have.”

Some of this behaviour is out of character. We can’t explain some of her behaviour that day

Mr Buckley said officers had “some indications” of why Ms Lord left work more than hour before she was scheduled to finish.

He told reporters: “We’ve got some indications as to why she behaved the way in which she did but what we’re doing is we’re just working backwards now to actually truly understand what may have taken place.

“We’re just cautious of everything we know at the moment because clearly we’ve ended up in the situation we have, which is not usual.

“I don’t think any of the conversations we’ve had are completely informing us as to why her state of mind ended up being what it was.”

Asked if officers were considering anything about her medical history, he said: “We would always consider it but there’s nothing that changes our approach at the moment.”

Mr Buckley said the CCTV footage they have collected did not reveal anything about the motivations for Ms Lord’s actions.

He said: “Some of this behaviour is out of character.

“We can’t explain some of her behaviour that day.

“We’re working really closely with family, with friends, with anybody else who might have had contact with her in the recent days or weeks to try and understand why this might have happened.”

He said officers are supporting her family, adding: “People are very shocked by what’s happened. Nobody knows why she’s done what she’s done.”

The newly released clip shows Ms Lord, wearing glasses and a long coat, walking along St Augustines Street in Norwich, which is busy with passing traffic, at 4.01pm on Friday.

Norfolk officers have said that her clothing, mobile phone, glasses and jewellery, including two rings, were discovered at various locations in the park.

A huge search is ongoing by specialist divers, who the force said are working in an “extraordinarily challenging environment”.

Mr Buckley said it will take “a couple of days” or longer to complete the search of the stretch of river, which has included using a range of sonar equipment.

He said: “It’s very, very challenging. The river is very, very full of water with all the rain, full of lots of debris. The divers can see about one foot in front of them.

“So it’s an extraordinarily challenging environment for them to work in so it’s slow, methodical at the moment, working with equipment and it will take probably a couple of days to get to a position where we’re kind of content with what we’ve done. It may even be longer.”

Mr Buckley said the force was keeping an open mind about what happened to Ms Lord but “everything we know is pointing to a high probability that Gaynor went into the water”.

But the senior officer said: “Nobody’s seen her go into the river, nobody’s seen her go into the water. But we know she ended up in the park.”

Mr Buckley also confirmed his team has consulted officers from Lancashire Police who worked on the search for Nicola Bulley.

Ms Bulley’s body was found in the River Wyre, in Lancashire, on February 19.

The Lancashire force was criticised over its handling of that investigation and the disclosure of Ms Bulley’s personal information.

The CCTV footage released earlier this week shows Ms Lord jogging up the cobbled Bedford Street after leaving work at the Bullards Gin counter in Jarrolds department store at 2.45pm, more than an hour before her shift was due to end at 4pm.

She was wearing a white shirt and a yellow tank top, and was carrying her large olive-coloured coat under her arm.

She can be seen on the footage walking in to London Street at 2.47pm and then crossing the road in Queen Street without waiting for a red light, narrowly missing moving traffic, heading towards the cathedral.

Around 30 minutes later, at 3.22pm, video shows Ms Lord putting her jacket on as she walks away from Norwich Cathedral.

At 3.49pm, CCTV captured her walking along St George’s Street near to the Playhouse theatre.

She then walked along St Crispins Road towards Pitt Street at 3.53pm.

Ms Lord is described as white, 5ft 6in, and has a blonde shoulder-length bob.