Mobile phone data could prove crucial in providing clarity on the deaths of two children and their mother who were found in their home in Ballinteer, south Dublin last week.
Seema Banu (37), her daughter Asfira Riza (11) and son Faizan Syed (6) were located in their house in the Llewellyn estate last Wednesday after neighbours became concerned having not seen them for days.
Following post-mortems, the deaths of the two children are being treated as murder, while the death of Seema is still being investigated after the post-mortem proved inconclusive.
Ligatures were found close to each of the bodies, it is understood. Further medical examinations on Ms Banu's remains are expected to be carried out in the coming days.
Gardaí in Dundrum have established a "person of interest" in the case who was known to the woman and the two children.
He met gardaí by appointment with a solicitor last Thursday. He has given two voluntary statements to gardaí but since Friday has declined to cooperate fully with gardaí because he is in a distressed state.
Security sources said the case is "complex" and that the exact picture still remains unclear.
"Either this is a personal tragedy and there is no one alive who is responsible. The other alternative is that someone else is responsible for these three deaths. Gardaí are trying to establish which scenario unfolded," a senior source said.
It is understood experts are examining mobile phone location information to see if it could put the person of interest near the scene around the time it is believed the children and their mother died.
When gardaí broke into the house on Wednesday they discovered a tap had been left running in an upstairs bathroom which had caused extensive flood damage.
Investigators are trying to determine if the running tap was intended to destroy evidence or, as in other murder-suicide cases, it was deliberately left running to alert neighbours in the aftermath of the tragedy.
The family of Ms Banu spoke from India about the tragedy and described the mother-of-two as the heart of the family.
Speaking from Ms Banu's hometown, a remote village in southern India, her cousin Sufi Masood told RTÉ News the family were in deep shock over the news. Mr Masood was translating on behalf of Seema's father Abdul Ghaffar and her mother Qurishid-un-nisa.
"She is like the heart of the family. For everyone, especially for the kids, they want to see them, everyone is here and they want to see them and feel them for at least the last one time," he said.
"We are feeling helpless that we couldn't do anything."
He said Ms Banu, who was one of eight children, took most of the decisions for the family and took great care of everyone.
During the last video call they had with her last week, she had taken time to speak to several members of the family, he said.
The family are appealing to the Irish Government to help pay for the repatriation of her remains and those of her children to India.
However, the Indian Ambassador to Ireland, Sandeep Kumar, has said the embassy also needs to hear what Seema's husband Sameer Sayed wants to do.
"The processes are still unfolding. We are definitely there to assist and offer support on all issues and we are confident all concerns will be addressed and there would be no need for fundraising," said the ambassador.