A lifeboat and helicopter have been deployed to search for a missing angler near Burniston, just north of Scarborough in North Yorkshire.
Police searching for missing York student Megan Roberts have said say the most probable scenario is that she "entered the river" while "heavily affected by alcohol".
Superintendent Phil Cain described the last known movements of the York St John University student almost a week after the 20-year-old went missing in the city.
Mr Cain said: "The strongest and most probable line of inquiry being pursued by police is that Megan, affected by alcohol, has entered the river."
Megan, who's 20, was last seen in the early hours of last Thursday morning while out with friends on Rougier Street near Lendal Bridge in York.
Police divers have arrived to start an underwater search for the missing York student, Megan Roberts.
It is understood a team of divers is planning to search a stretch of the River Ouse around Lendal Bridge.
A one hour search was carried out on Tuesday afternoon before darkness fell, with more extensive searches are expected today.
Megan, 20, a Fine Arts student at York St John University has not been seen since the early hours of last Thursday morning, after a night out with friends in the city.
Police are increasingly concerned for her welfare.
Volunteers are going to be in York city centre today as part of the search for the search for missing Megan Roberts.
They will be encouraging businesses to put up posters and share messages on social media sites. Megan, who's 20, was last seen in the early hours of last Thursday morning while out with friends on Rougier Street near Lendal Bridge.
Missing People Local Campaigns Manager Martin Crosby said: “Our thoughts are with Megan’s family at this very difficult time and we hope that our efforts will help to bringing her home safely.”
“Please join the search – get in touch and come and help us if you are in the Lendal Bridge area on Wednesday and help us spread awareness of the appeal for Megan."
Police appear to have ruled out any suggestion of criminal activity following Miss Roberts' disappearance.
In an interview with Sky News, Mr Cain denied there was any suggestion that a man had been following the student in the hours before she was last seen.
He said: "There were some Twitter comments on Megan's account but we've explored those with family and friends and at this stage there's nothing to suggest there is any criminality involved in relation to Megan's disappearance."
Mr Cain said police have since begun interviews with Miss Roberts' friends to establish her last known movements.
He said: "There's nothing to indicate Megan was anything other than a bright young student."
The York St. John University, where missing girl Megan Roberts is a student, have said they are hopeful she will be found safely:
Our thoughts are with Megan’s family and friends at this distressing time; however, we remain positive and are hopeful of a positive outcome to the situation. As soon as the University was informed that Megan was missing it began providing support for Megan’s fellow students as well as working with the police to support their enquiries.
Police investigating the disappearance of missing student Megan Roberts are searching the River Ouse in York.
The 20-year-old was last seen on CCTV with a group of people on the corner of Rougier Street near Lendal Bridge at around 2.20am on Thursday.
The group were seen a short time later at the other side of Lendal Bridge but Megan was not with them.
Officers are appealing to anyone who saw a woman matching her description in the early hours of Thursday morning to get in touch.
Missing University student Megan Roberts was last seen with a group of people shortly after leaving a nightclub in York, police have said.
Police officers reviewing CCTV have established that Miss Roberts was with a group of people on the corner of Rougier Street near Lendal Bridge at around 2.20 am.
The group were seen a short time later on the other side of Lendal Bridge, on Museum Street but Megan was not with them.
The disappearance of a University student in York who has not been seen for four days has been described as "very out of character" by police.
Megan Roberts, who is a student at York St John University, was reported missing by her mother after a friend raised concerns.
- The 20-year-old was last seen at around 2am on Thursday in the Popworld bar, on George Hudson Street in York
- She is described as 5ft 6in and of medium build with long, dark brown hair
- Last seen wearing a cream knee-length dress which had large brown and orange flowers on it with black plimsolls-type shoes
Friends of university student Megan Roberts have appealed for information to help find the missing 20-year-old.
Ms Roberts, a student at York St John University, was last seen at around 2am on Thursday in the Popworld bar, on George Hudson Street in York.
One of Megan's friends, Rockie Thorley wrote on Facebook: "Please raise awareness. There are some very concerned friends and family that just want to see her return home safe!
"Devastating to see such a happy face of a very close friend when it is involved with a missing persons investigation please if anybody knows anything contact the police."
Another wrote: "A girl I've been in school with since year 5 till high school, Megan Roberts has been missing for 5 days now please share the links of her for me and everyone else that would love to see this lovely girl come home to her family and friends safe and sound."