Police have confirmed the cause of death of 15-year-old Allison Marimon-Herrera in Newry was strangulation.
The cause of the death of her mother Giselle has not been confirmed, however detectives believe there is a strong possibility she too was strangled.
Results of a post mortem on the body of a 38-year-old man, who police believe was Giselle Marimon-Herrera's partner and who also lived at the Glin Ree Court, Newry apartment, have concluded that he died by hanging.
The man has not yet been named by police.
Ms Marimon-Herrera was from Colombia and had lived in Northern Ireland for around four years.
Her daughter Allison was born in Spain and had lived in Northern Ireland since 2017. She attended Newry High School.
They were all found dead at a flat in the Glin Ree Court area on Thursday.
Detective Superintendent Murphy said that he believed Giselle and Allison were still alive in the early hours of Sunday morning but family members had been unable to contact them since.
"The exact circumstances of what happened in their home remains the subject of our investigation," he said.
"I would appeal today to anyone who came into direct contact with either Giselle or Allison or communicated with them via text or social media since Friday to contact detectives in Newry.
"We are currently supporting the families of those involved as well as Newry High school. I would ask that they are given the time and space to come to terms with these tragic events."
Police have confirmed that it was not currently seeking anyone else in connection with the deaths.
Initial reports suggested detectives were treating the incident as a suspected double murder and suicide, but this has not been confirmed.