Michael Snelling, 59, was detained at his mother’s house in Tyneside on Tuesday morning in the first arrest made by North Yorkshire Police over the chef’s disappearance five years ago.
But after being quizzed for more than 24 hours by detectives he was last night released on conditional bail, the force confirmed.
Snelling, who lives less than a mile from Miss Lawrence’s former home in York, was a colleague of the chef and worked at the University of York’s biology department before starting work at a mental health charity.
Police yesterday set up a forensic tent in the back garden of his semi-detached home in Burnholme Grove, York, though a sniffer dog and investigators left the property late in the afternoon.
Searches were also going on at his mother’s house in North Shields, Tyneside, which Snelling is understood to regularly visit.
A North Yorkshire Police spokesman said: “Forensic searches at relevant properties are expected to continue for a number of days.
“Every effort will be made to minimise disruption to local residents and the public affected by this work.
“North Yorkshire Police would like to thank those people for their patience and understanding.
“As investigations continue with the possibility of further arrests to be made, all sections of the community and the media are reminded and encouraged to respect the rights of others, including those connected to the case.”
Miss Lawrence, who worked in a kitchen at the University of York, was 35 when she was reported missing by her father on March 20, 2009.
Announcing the arrest on Tuesday, North Yorkshire Police said this did not mean her body had been found, adding that the force “cannot rule out the possibility of further arrests in the future as the review continues.”
The missing chef’s father said yesterday that the first arrest in the five-year investigation into his daughter’s disappearance could prompt witnesses to come forward with potentially vital information.
Martin Dales, a friend and spokesman for Miss Lawrence’s father Peter, stressed the public could still have vital information that could help the inquiry.
He said: “The media coverage is an opportunity for people to be reminded of the essential need for information to keep flowing in.
“People might well have had their memories stirred by this. There must be a lot of people out there who ought to be speaking with the police. We need to get people to engage with the police.”
Mr Lawrence has suffered “quite a shock” since he was told of the first arrest in the search for his daughter, Mr Dales said.
There had been others in the five years since she disappeared, including the discovery of a body in 2009 which turned out not to be Miss Lawrence.
Miss Lawrence was 35 when she was reported missing by her father on March 20, 2009. She was last seen around 3.05pm on March 18, walking back to her home, and that night she spoke to both her parents on the phone.
North Yorkshire Police launched a review of the original Claudia Lawrence investigation last year after a new major crime unit was established by the force.
Last year, the new investigation team conducted a detailed, two month re-examination of Miss Lawrence’s home.
Then, in March this year, senior officers announced a series of new lines of inquiry on the fifth anniversary of her disappearance.