Caroline Glachan, 14, was brutally attacked and her body was found on the banks of the River Leven in West Dunbartonshire on 25 August 1996.
She had suffered blunt trauma to the head and drowned.
Despite extensive investigations, no-one has ever been arrested in connection with her murder.
Two decades on from her death, Police Scotland made a fresh appeal for information on the BBC’s Crimewatch programme on Monday night and received about 20 calls in response. Officers hope it will help them identify a hooded man who was spotted in the area on the night of the murder.
Detective Superintendent Jim Kerr said: “More than 20 calls were received and the information given to police will now be followed up by the officers from the homicide governance and review team, and I am hopeful that some calls could assist with the investigation.”
Caroline’s mother Margaret McKeich, 60, told the programme how she remembers the day. She recently attended a press conference in which she called on the community to reveal the killer.