A fourth victim has been reported dead in a ferocious house fire in Fermanagh, a detective investigating the claim said.
Police Service of Northern Ireland (PSNI) officers are working "intensively" to establish how many were involved in Tuesday's early morning blaze at a whitewashed bungalow near Derrylin.
Three have been confirmed dead but it may take several days to identify all victims because of the scale of damage to the property and poor weather.
A man aged 27 arrested by police at the scene on suspicion of murder remains in hospital under guard.
Inspector Peter McKenna said: "I am aware of local information about a family living in this property and reports of a fourth victim.
"At this stage we are still working intensively to establish how many victims were involved in this appalling incident."
He said the fire was started deliberately.
"It was ferocious and has left a very complex crime scene.
"However, we have specialist search and rescue teams working hard to try and identify those who died."
This will take a number of days due to the structural damage caused by the fire which is further compounded by predicted severe weather, the senior officer added.
He said: "The specialist officers will ensure that the bodies of all persons identified are recovered in a dignified manner.
"Post-mortem examinations will then follow and this will assist me in confirming the identity of the victims."
Neighbours used a sledgehammer in a desperate bid to break in and rescue the victims on Tuesday.
They were unable to get in and save generations of the family.
The rural bungalow near the border with the Irish Republic was destroyed in the blaze and the roof collapsed, leaving a shell surrounded by farm buildings and machinery.
The victims only moved to the area recently, a local priest said, and were members of one family.
They had previously lived in the Republic and were originally from England.