A teenage girl who was found dead alongside the bodies of her mother and a man in a flat in Newry, County Down, had been strangled, police have said.
The bodies of Allison Marimon-Herrera, aged 15, and her mother Giselle, aged 37, were discovered by police who forced entry to the flat on Thursday.
The 38-year-old man who was also found dead has yet to be identified.
Detectives have started a murder inquiry but are not seeking anyone else in connection with the deaths.
The Police Service of Northern Ireland (PSNI) released details on Friday night of the post-mortem examinations of the three bodies.
The results were "not definitive" about the cause of Ms Marimon-Herrera's death but there was a "strong possibility" that she was also strangled, police said.
A post-mortem examination showed that the man died by hanging.
Police believe he was the woman's partner and lived in the same apartment block at Glin Ree Court in Newry.
Police went to the flat after a relative reported concerns that they had not been in contact with a family member for days.
The bodies were found at about 11:00 GMT on Thursday.
Officers said they believe Ms Marimon-Herrera and her daughter Allison were still alive on Sunday morning.
Det Supt Jason Murphy said Ms Marimon-Herrera was originally from Colombia and had arrived in Northern Ireland about four years ago.
He said her daughter was born in Spain, had lived in Northern Ireland since 2017 and was a pupil at Newry High School.
"This is an unspeakable tragedy," he added.
"I believe that Giselle and Allison were still alive in the early hours of Sunday morning but family members have not been able to contact them since.
"The exact circumstances of what happened in their home remain the subject of the investigation."
Newry High School principal Iestyn Brown said that the school was "deeply shocked and saddened to learn of the passing of our year 11 pupil Allison".
"Allison was a talented, kind, courteous and well-mannered pupil with a beautiful smile," he said.
"Both staff and pupils are profoundly saddened by her death and she will be remembered with great affection by her fellow pupils and staff alike.
"Our hearts go out to Allison's family circle - they are foremost in our thoughts and prayers at this sad time."