Missing student Megan Roberts probably fell into the river while she was "affected by alcohol", police have said, as underwater divers continue searching for the 20-year-old.
The York St John University student was last seen almost a week ago in the early hours of Thursday morning after a night out at the Popworld nightclub. CCTV footage shows Megan standing near Lendal Bridge in York city centre at 2.20am with a group of people. The group was seen a short time later on Museum Street, but without Megan.
Superintendent Phil Cain said: "The strongest and most probable line of inquiry being pursued by police is that Megan, affected by alcohol, has entered the river."
20-year-old Megan was last seen in a nightclub last Thursday
An underwater search unit and specialist officers are carrying out searches along the River Ouse for the second day, after Tuesday's efforts proved fruitless.
On Tuesday, The Huffington Post UK revealed Megan had tweeted about being stalked by a "creepy man", who followed her and a friend to a pub shortly before her disappearance.
On 16 January Megan visited two pubs with a friend, and tweeted:
North Yorkshire Police say they are aware of the tweets. Superintendent Cain said: "We are exploring with friends who are aware of a Twitter message, which was commenting around a male in a bar where Megan was at the time.
"Friends are convinced there was nothing to suggest Megan was being stalked at that stage. We do not believe that is connected to Megan's disappearance.
"At this moment in time there's no suggestion of any criminality whatsoever and we are treating this as a missing from home."
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Megan is described as white, around 5ft 6in tall, of medium build with long dark brown hair. When she was last seen she was wearing a cream knee length dress which had large brown and orange flowers on it and black plimsoll type shoes.
Cain added: "We are very concerned for Megan's welfare and are urging the public to help us establish her movements in the early hours of Thursday.
"Her disappearance and the fact she has not had any contact with her family and friends for almost five days now is extremely unlike her.
"Megan's family are understandably very distressed."