A detective investigating the disappearance and suspected murder of chef Claudia Lawrence said he is "actively pursuing new leads" on the sixth anniversary of the day she was last seen.
Detective Superintendent Dai Malyn, of North Yorkshire Police, said his team had made "significant progress" since the force began reviewing the case in 2013 and may make more arrests in the coming weeks and months
He urged anyone who has not yet revealed information about their relationship with Miss Lawrence or the events in the days leading up to her disappearance to come forward or risk being arrested.
Miss Lawrence was last seen on March 18, 2009, and was reported missing by her father on March 20 after concerns were raised when she failed to arrive for her 6am shift at York University.
A number of new searches have been carried out since 2013, including a detailed re-examination of Miss Lawrence's house in the Heworth area of York and a fingertip search of the alleyway that leads to the back of the building.
Last year a 60-year-old man was arrested in connection with her disappearance and suspected murder, but was later released without charge.
A 47-year-old man remains on bail on suspicion of perverting the course of justice.