Next Wednesday marks the 18th anniversary of the disappearance of Hebden Bridge schoolgirl Lindsay Rimer.
The 13-year-old left her home in Cambridge Street to buy cornflakes but never returned.
Her body was found five months later in Rochdale Canal.
Police say they have never stopped investigating what happened to Lindsay and are appealing for anyone with information that may help their inquiry to get in touch.
Detective Superintendent Colin Prime, of West Yorkshire Police’s Homicide and Major Enquiries Team, said: “The murder of Lindsay Rymer is one of a number of historic cases which we are continuing to periodically review in line with national guidance to see if advances in forensic science can help develop new lines of enquiry.
“The case will never be closed by West Yorkshire Police until it is solved and I urge anyone who may have information which could help us find Lindsay’s killer to contact us.”
Lindsay, a pupil at Calder High School at the time, had left for the Spar supermarket in Crown Street at around 10pm on November 7, 1994.
Police know she called in to the Trades Club in Holme Street on her way to the supermarket and, according to the CCTV footage in the supermarket, Lindsay paid for the cornflakes at 10.22pm.
That was the last time she was seen alive.
On Wednesday, April 12, 1995, her body was recovered from the Rochdale Canal, approximately a mile upstream from Hebden Bridge town centre.
Anyone with any information which could help the inquiry should contact police on 101 or Crimestoppers, where information can be passed on anonymously, on 0800 555111.