After two men died at a hostel for the homeless in west Belfast early yesterday a fire officer said there was no sign it was started deliberately.
Three other men were taken to hospital suffering from smoke inhalation.
The fire at the Morning Star men's hostel on Divis Street began around 2.30 a.m.
There were 18 people, including staff, in the building at the time. The hostel is run by the Legion of Mary and owned by the Northern Ireland Housing Executive.
Mr Hugo Brannigan (62) and Mr Jim Irvine (42) died in the fire. The remaining residents are recovering at the Welcome Centre at St Peter's Cathedral. Local priest, Father Joe McGuigan, who was called to the scene at 3 a.m., broke the news to the family of one of the dead men.
"They are devastated and especially because there was a room at home for him. But that it not how he decided to live," he said.
Sinn Féin president, Mr Gerry Adams, said the remaining residents must be housed somewhere "they will not be placed in any further danger".
SDLP Assembly member, Dr Joe Hendron, offered his condolences and paid tribute to the efforts of local people to contain the fire.