Three men have been arrested on suspicion of the murder of missing chef Claudia Lawrence, North Yorkshire Police said on Wednesday.
The York University chef was 35 when she disappeared six years ago on March 18.
Police said the men are in their 50s and from the York area.
She was reported missing by her father Peter after concerns were raised when she failed to turn up for her 6am shift at the university.
A York man in his 50s who was arrested in March remains on police bail.
Police said Miss Lawrence has not been found.
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 York, and a fingertip search of an alleyway that leads to the rear of the house.
They have also issued previously unseen CCTV footage of two people walking near the house.
The new arrests, and the arrest in March, are understood to be linked to these lines of inquiry.
New searches are being carried out in the area and are expected to last several days.
A 60-year-old man was arrested last year in connection with her disappearance and suspected murder but was later released without charge.
And a 47-year-old man arrested last July on suspicion of perverting the course of justice has also been released with no further action taken.
Detective Superintendent Dai Malyn, head of North Yorkshire Police's major crime unit, urged people not to identify the men who have been arrested to prevent the investigation being "compromised or potentially damaged in any way".