Police investigating the murder of three family members north of Adelaide say they have obtained a DNA profile of an unknown man from the crime scene.

Chantelle Rowe, 16, and her parents, Andrew and Rose, were found dead a week ago in a house at Kapunda, 76 kilometres north of Adelaide.

The victims had multiple wounds.

Detective Superintendent Grant Moyle says a DNA sample from the crime scene does not match anyone in the national database.

He says voluntary testing of some people in the town has also failed to produce a match.

"We are speaking to all the male youths that associated with the family," he said.

Police are also looking for a white Toyota Landcruiser that was seen in the street around the time of the murders.

Police say the trio was killed sometime between the night of November 7 and the early hours of the following day.

They had moved there just months ago from another property in the town.

Police also believe only one person was in the house when the mother, father and daughter were killed.

Pictures of the family were released last Friday in the hope it would help to establish their movements in the hours before their deaths.

Police and forensic investigators have been working at the house in Harriet Street since the bodies were found.

Police have also sifted through a dump about 70 kilometres north of the crime scene and failed to find the murder weapon.