Two men who were arrested in March over the disappearance of Bath hospital worker Melanie Hall have been released without charge.
Miss Hall disappeared after a night out in Bath
The men, both in their 30s and from the Bath area answered their bail and were released without charge, said Avon and Somerset Police.
Searches at sites in and around Bath throughout March failed to produce vital clues and detectives admitted they had had no response to an appeal for a key witness to come forward.
Miss Hall, from Bradford Leigh, near Bradford on Avon, went missing from Cadillac's nightclub in the centre of Bath in June 1996.
She was aged 25 at the time.
Detective Chief Inspector Barrie Douglas said: "The new information we received into the disappearance of Melanie has been investigated thoroughly, methodically and professionally by a team of officers over the past six months.
"As part of these new lines of enquiry two men were arrested. After further investigations and discussions with the Crown Prosecution Service these men were released without charge.
"This has been a difficult enquiry because of the length of time since Melanie disappeared. This has affected the available forensic examinations of items and locations."
In May this year, detectives admitted the high-profile investigation into Miss Hall's disappearance might prove fruitless.
Neither of the men arrested was her boyfriend.