Claudia Lawrence was last seen at her work at Goodricke College
A missing university chef may have "come to some harm", detectives investigating her disappearance have revealed.
Claudia Lawrence, 35, was last seen by colleagues at the University of York's Goodricke College last Wednesday.
Det Supt Ray Galloway said she had not been in touch with family or friends since 2030 GMT that night and appealed for the public's help.
He said his "professional judgement is that she has probably come to harm".
Speaking a week after her disappearance, Det Supt Galloway said: "At the moment, we have no tangible evidence of a crime and I really do hope that Claudia is out there and that she makes contact."
Miss Lawrence was last seen at about 1400 GMT when she left the college, where she worked as a chef.
She was later spotted on CCTV as she walked the three-mile route to her home in Heworth Road.
Police news conference on Miss Lawrence's disappearance
The officer said he believed Miss Lawrence was with someone she knew.
He said she had recently been walking to work after her car broke down but that it would be "unlikely" for her to get into a car with a stranger.
"I would really like to encourage people to tell me little snippets of what they know," he said.
"What do they know about Claudia? She was a young, single woman. Did she have a new boyfriend? Did anyone see her in an unusual vehicle? Was she in a pub that she didn't normally frequent?
"Just that little snippet would help me to just contextualise what I know."
The officer said she did not appear on any CCTV footage from her normal route to work on Thursday.
It was believed Miss Lawrence had left home to walk to work at around 0530 GMT on Thursday but the officer said it was not known if she had gone missing on Wednesday evening.
He described her as a "prolific texter" who was always in contact with her family.
Addressing the public he said: "We have no information to her whereabouts after 2030 GMT.
"Try to help me fill that gap, I need the public's help."
Earlier, her father Peter Lawrence said the past few days had been a "living nightmare".
He said: "There is no reason for Claudia to be missing. She had no reason to go, no problems, no troubles."
Miss Lawrence is described as 5ft 6in (1.7m) tall and slim, with brown hair. She was last seen wearing a white T-shirt, blue jeans and trainers.
Police are appealing for help to find a small blue or green rucksack which she used to carry her chef's whites to work.