A man has been arrested on suspicion of the murder of Melanie Hall, who went missing after a night out with friends in Bath in 1996.
Police detained the 45-year-old man on Thursday and he remains in custody for questioning.
Ms Hall, 25, was last seen sitting on a stool at the edge of a dance floor at Cadillacs nightclub in Walcot Street in the early hours of 9 June, 1996.
Her remains were discovered by a workman off the northbound slipway at junction 14 of the M5 at Thornbury, Gloucestershire, in 2009.
Ms Hall's remains were found near the M5 at Thornbury in 2009
Earlier this month Ms Hall's parents offered a £50,000 reward for information leading to the conviction of the person or people responsible for her murder.
Detectives also revealed they had received "potentially significant information" following an appeal on a BBC Crimewatch programme on the 20th anniversary of her disappearance.
Announcing the reward this month, Steve Hall said: "The loss of Melanie has been life-changing for us and we'll never be the same people as we were before Melanie disappeared.
"Melanie's murder has had a terrible impact on our family and I know my wife Pat is tortured by what happened to our daughter, and will never get over it."
Steve and Pat Hall offered a reward for information earlier this month
Detective Superintendent Andy Bevan said: "Melanie's parents have been informed of the arrest and will continue to be supported and updated on the progress of our inquiry by specialist family liaison officers."
Police have previously arrested nine people in connection with the case but nobody has been charged.