A father and five children are believed to have been killed in a house fire which three other children escaped from, police have confirmed.
The fire at Llangammarch Wells, Powys, broke out in the early hours of Monday.
Three children aged 13, 12 and 10 escaped but five others aged between four and 11 years are missing, presumed dead.
Dyfed-Powys Police confirmed at a press conference on Tuesday that all of the victims are related.
Father David Cuthbertson is thought to have perished in the fire - and a family friend said his son-in-law was one of the first firefighters on the scene.
Mr Cuthbertson, a 68-year-old retired builder, lived in the rented farmhouse with his children.
Family friend Mary Ann Gilchrist said she first met Mr Cuthbertson 26 years ago and described him as "charismatic and utterly charming".
"When you realise it is real, it is devastating. What I find so horrific is that one of the people who was responding was his [Mr Cuthbertson's] son-in-law," she said.
"It has just been a horrific shock, especially when it involves so many children."
Police said the investigation was likely to go on for weeks, including the recovery of the bodies.
"Based on current information available to us, we are working on the hypothesis that one adult male and five children, aged between 11 and four years old, are unaccounted for and believed to be deceased within the house," said Dyfed-Powys Police's Supt Jon Cummins.
"Due to the severity of damage at the scene we are unable at this stage to identify any of the deceased."
Supt Cummins said the three children who escaped were taken to hospital but were not in a life-threatening condition.
"Specialist scientists and fire investigators continue to assess the scene, which is very complex and perilous," he added.
He said the cause of the fire was being treated as unexplained and added that the family had asked for privacy.
Local councillor and school governor Tim Van-Rees said: "He clearly was a devoted father, the children were his life."
Mr Van-Rees said he had been in touch with social services to help the surviving children and support was being put in place in schools to help pupils deal with the tragedy.
"There will be vacant places on school buses, several vacant places... we need to make sure that all local services do their best to support children and the community," he said.
"This is a tragedy which is frankly unprecedented."
A book of condolence has been set up in St Cadmarch's Church in Llangammarch and Reverend Petra Beresford-Webb has set up an area for people to leave flowers.
Ms Beresford-Webb said: "I think it is important for people to be able to get their feelings out in some way."
Floral tributes have been left at the end of the drive to the shell of Pointyn Farm and a collection bucket has been started for the surviving children in the village post office.
Nic North, BBC Wales News in Llangammarch Wells
Llangammarch Wells is in shock as it awaits official confirmation of what many believe they already know.
Few in this tightly-knit community are in any doubt about the identity of those who perished in the midnight blaze at the farmhouse.
On Monday, the village of less than 500 people woke to a thick fog that concealed the smoke still billowing from the wrecked building high on the side of a valley above the village.
The tight-knit community have begun laying floral tributes at the foot of the hill where the tragedy happened.
A message beside a bunch of chrysanthemums reads: "Such a terrible tragedy. Special thoughts to family and friends."
Neighbour Ron Birchall, 73, described Mr Cuthbertson as a "great guy" who "loved his kids".
First Minister Carwyn Jones tweeted: "Very saddened by the horrific fire at Llangammarch Wells. My thoughts are with all those affected by this heart-breaking tragedy."
Local MP Chris Davies said the community was "devastated" by tragedy and that the family were "well known in the community".
He said the community had come together in the aftermath of the fire, adding: "The effects of this will be felt for many years to come in Llangammarch."
Llangammarch Wells fire: As it happened
Local AM Kirsty Williams praised emergency services and volunteer fire fighters who were first on the scene, saying they had done everything they could to save lives.
"They themselves are part of this community, they would have known, I'm sure, the family that was affected... it is just tragic they were not able to save more people," she said.
A fundraising page set up to help the family has so far raised more than £10,000.
One of numerous tributes left on the page said: "We lived in Cwm Deri until July of this year and knew all of the children well, all beautiful inside and out with a devoted daddy - we are heartbroken."