A man has been arrested on suspicion of murdering missing chef Claudia Lawrence.
The man, aged in his 50s and from the York area, was arrested today, North Yorkshire Police said.
Miss Lawrence was last seen six years ago on March 18, 2009.
A police spokesman said searches are being carried out in relation to the York University chef's disappearance and are expected to continue for a number of days.
He said Miss Lawrence, who was 35 when she went missing, had not been found.
Miss Lawrence's family have been told about the arrest and are being supported by trained officers, police said.
Detective Superintendent Dai Malyn, of North Yorkshire Police, urged people not to identify the arrested man.
He said: " To ensure the investigation and legal process are not compromised or potentially damaged in any way during this critical phase in seeking the truth about Claudia's disappearance, North Yorkshire Police strongly advises the media and members of the public against identifying the man who has been arrested.
"This includes naming or publishing images of the man on traditional media platforms or social networking sites.
"I urge everyone to show restraint and patience while we carry out these very important inquiries."
Miss Lawrence was reported missing by her father after concerns were raised when she failed to turn up for her 6am shift at work on March 19 2009.
North Yorkshire Police began reviewing the case in 2013 and have since carried out a number of searches, including a detailed re-examination of Miss Lawrence's home, in the Heworth area of the city, and a fingertip search of an alleyway that leads to the rear of the house.
A 60-year-old man was arrested last year in connection with her disappearance and suspected murder but was later released without charge, while a 47-year-old man remains on bail on suspicion of perverting the course of justice.
Mr Malyn said he is "actively pursuing new leads" and that his team had made "significant progress" since the force began reviewing the case in 2013.
The detective said some people locally knew Miss Lawrence but have kept their relationship secret and some have deliberately lied about a number of issues concerning their association with the chef.
Last week, on the sixth anniversary of her disappearance, police released previously unseen CCTV footage of two people seen walking near the chef's home on the evening she went missing.
Speaking in York on the anniversary, Miss Lawrence's father, Peter, recalled that he last spoke to his daughter on the phone.
He said: "To have had six years without her company, without her chat, her smile, her laugh, meeting her for a drink, days out and meals out - it tells. I just miss that companionship, that love so much that it just really hurts so much.
"It galls me that someone out there knows what happened to Claudia but has not said anything."
He added: "Six years on, it does not get any better. All we can hope is that we find out what happened to Claudia. If she was murdered, as the police believe, then I want to be able to bury her.
"As I have been saying for six years, it's the not knowing that makes it worse and it means that the family just cannot move on at all."
Today, Mr Lawrence said: " It is encouraging to know that, following all the media activity over the last three weeks, from Claudia's 41st birthday to the sixth anniversary of her being missing, North Yorkshire Police continue to be active in seeking answers as to what has happened to Claudia.
"It is to be hoped that the matter can be resolved as soon as possible and I encourage people to continue to come forward with information to the police."
Anyone with information that could assist the investigation is asked to contact North Yorkshire Police on 101 or Crimestoppers anonymously on 0800 555111 or www.crimestoppers-uk.org.
Members of the media gathered outside Miss Lawrence's home on Heworth Road today.
Speaking outside the terraced house, Martin Dales, Mr Lawrence's friend and spokesman, said: "I'm pleased the police are active and their activity has produced a result of some description. Obviously it's down to them as to where it goes and they must be left to do their work on the matter.
"There's been a huge amount of activity in the last three weeks in particular, from Claudia's birthday right up to the sixth anniversary."
He continued: "As yet there have been no charges on anybody and six years is a long time without any answers so I think people have got to be a bit more human about this. There are people obviously withholding information and they need to really examine their consciences. Whatever trouble they've been in the family need answers."
In another area of York, police could be seen searching a semi-detached house in a quiet cul-de-sac.
Two police community support officers and police vans were stationed at the entrance to the road, which contains 10 houses.
Officers entered and left the house throughout the afternoon and spent some time searching in the detached garage.
No-one else appeared to be at the property and the curtains were drawn in the bay windows to the front of the building.
Neighbours said they believed a man lived in the house with his wife.
One woman, who did not want to be identified, said: "They're a nice couple. I was really surprised, really shocked to see the police searching the house.
"This is a nice road, we all look out for each other."
A man, who said he had just moved to the street, said: "I don't really know the man. He keeps himself to himself.
"This is not what you expect to come home to."
Another man said: "Police have been sniffing around this area for the past six years."