Caroline Glachan, 14, was brutally attacked and her body was found on the banks of the River Leven in West Dunbartonshire on August 25 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: “We have received a positive response following last night’s appeal on the Crimewatch programme.
“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.
“Anyone with information should contact the Operation Fairing team through 101 or email officers on [email protected] Alternatively contact Crimestoppers on 0800 555 111, where anonymity can be maintained.”
Caroline’s mother Margaret McKeich told the programme how she remembers the day.
‘’I looked out the window and there was a police officer with a police woman and I knew. I just knew,” she said.
“I got this unbelievable pain, which I can still feel, just a pain in my heart. I just knew it was her.
‘’They came up and they asked about her and the clothing that she had on. I told them and they said that they believed that it was her but they would have to identify her.
‘’Of course by this time it is my birthday, so life didn’t begin at 40. For me, it basically ended.’’
Mrs McKeich, 60, recently attended a press conference in which she called on the community to reveal the killer.
She believes locals know who is responsible for her daughter’s death and appealed for them to contact detectives.
Caroline, from Bonhill, was heading to meet her boyfriend in Renton, having spent an evening with friends, and took a short cut from shops along Dillichip Loan towards The Towpath and the Black Bridge.
On the Crimewatch show, the teenager’s best friend Joanne Menzies, one of the last people to see Caroline alive, returned to the area where they parted for the final time.
Urging those with information to come forward, Ms Menzies told the programme: ‘’Caroline was only a child, she was only 14.
‘’These people should now stand up and actually finally be counted as a human being and not hiding a sickening secret.’’