A man has been arrested on suspicion of the 1994 murder of 13-year-old Lindsay Rimer.
Police said the man was arrested at an undisclosed prison where he is serving a sentence for other offences.
The man, who is being interviewed today and tomorrow, is expected to be bailed and returned to prison while enquires continue.
Officers are also interviewing a number of potential witnesses in the Hebden Bridge and wider Halifax area.
Lindsay left her home to buy a box of corn flakes late during the evening of 7 November, 1994, but didn't return home.
Her body was then found in a canal close to her home six months later.
Following today's arrest, senior investigating officer, detective chief inspector James Entwistle, said: "We remain very firmly committed to doing everything we can to get ju