POLICE investigating the murder of German backpacker Inga Maria Hauser have received more than 30 calls from members of the public following a renewed appeal for information last month.
The body of the 18-year-old was found in Ballypatrick Forest outside Ballycastle on April 20 1988.
She had been seen travelling on the Stranraer to Larne ferry on April 6 1988.
Police believe she was murdered shortly after she arrived in Northern Ireland.
On the 30th anniversary of the murder last month, police made a new appeal for information.
The officer in charge of the investigation, Detective Chief Superintendent Raymond Murray, said officers believe they are "extremely close" to bringing the teenager's killer or killers to justice.
He said police are working to identify the man whose DNA was found at the crime scene. He said officers had received the results of further DNA screening and had met "scientists and other specialists in order to take these forward".
Ms Hauser's father has died since her murder and her mother has been ill for many years.
Her sister Friederike Leibl said the teenager's murder had left her family "broken inside".
"My father was worst hit - he fell ill with prostate cancer in 2005 and was treated for depression when the whole body was full of cancer," she said.
"The fact of being confronted with this murder for a lifetime is just cruel, sick, sick. So I ask you to come forward within formation, otherwise my sister's soul will never rest."
Detective Chief Superintendent Murray made a direct appeal to the family of the murder or murderers to contact them.
"If you are a family member who has information or who even assisted the killer or killers in the aftermath of the incident, search your conscience as now is the time that common humanity should override misplaced loyalty," he said.
