Detectives investigating the murder of Caroline Graham in Portadown in 1989 want a man who called them on Saturday to phone back.
The call came after the teenager’s mother made a renewed appeal for information in a press conference.
The man didn’t leave his name but Serious Crime Branch officers believe he may have important information.
He is asked to phone detectives on 02890 700 727 or 07585 22 82 83.
Any information will be treated in the strictest confidence.
New details on the night 19-year-old Caroline disappeared were also released last week.
Mrs Graham said she needed “closure” and to lay her daughter to rest.