The "iconic and unique" library at Glasgow School of Art has been lost in the fire which swept through the world-renowned building.
After an inspection of the Charles Rennie Mackintosh building today, the school revealed that the majority of the structure was "intact".
Broadcaster Muriel Gray, the art school's chairwoman, said the institution's archives had also been saved.
She said: "Bad news first is that we have lost the iconic and unique Mackintosh library. This is an enormous blow and we are understandably devastated.
"But the most amazing, almost miraculous news is that the majority of the building is still intact.
"Due to one of the most astonishingly intelligent and professional pieces of strategy by the fire services, they succeeded in protecting the vast majority of the building, apparently by forming a human wall of firefighters up the west end of the main staircase and containing the fire."
Earlier, the fire service said that around 90% of the building has been salvaged and up to 70% of its contents saved.
Smoke could still be seen rising from the charred windows of the school this morning - 24 hours after the flames took hold.
No-one was injured in the fire but art lovers, architects and famous former students spoke of their sorrow at seeing the building in flames.
The fire service has yet to confirm the cause of the blaze, which some students have suggested could have started in the basement when a spark from a projector caught a piece of foam.
As well as housing one of Europe's leading art schools, the listed Mackintosh-designed building is a tourist attraction in its own right.
Completed at the turn of the 20th century, it was voted as the best building of the past 175 years in a poll by the Royal Institute of British Architects (Riba).
Both the Scottish and UK Governments have pledged funding support to help any restoration work required to the building.
Chief Secretary to the Treasury Danny Alexander said Westminster would give "millions", if necessary, while Scottish Culture Secretary Fiona Hyslop said the SNP Government was committed to "strongly supporting the funding effort" required.
Ms Gray said the damage was "considerably less" than feared and although students have lost some or all of their work, many others had theirs preserved.
She said staff and curators would be able to enter the building to assess what could be salvaged in the next few days.
"The joy that our archives are safe combines with the delight in seeing most of our beloved building bruised and battered but most certainly not destroyed.
"As for the library, Mackintosh was not famous for working in precious materials. It was his vision that was precious and we are confident that we can recreate what was lost as faithfully as possible.
"Our main concern right now is the welfare of the students and the impending graduation and everyone is working hard together to achieve the best outcome for all."
She thanked the public for the "warmth of support" and said she had "run out of words" with which to thank firefighters.
"But the school has most certainly gained a new gallery of heroes" she added.
Speaking in Glasgow today, Mr Alexander said: "It's a hugely important building not just for Glasgow and Scotland but for the whole of the United Kingdom.
"I can tell you that the UK Government will be willing to make a significant financial contribution towards the cost of rebuilding.
"Obviously at the moment we don't know the precise extent of the damage or what the costs will be, so I can't put a figure on it, but the Chancellor and I have spoken this morning and we both think it is appropriate."
Pressed on what the UK contribution would be, Mr Alexander said: "We could make contributions in the millions if that is necessary."
The Scottish Government has already said it will do all it can to assist in the rebuilding of what is regarded as one of the finest architectural works in the UK.
Speaking after visiting the site today, Ms Hyslop said: "It was truly heartbreaking to see the Mackintosh Building in flames. We are all thankful that no-one has been hurt and for the heroic efforts of firefighters to safely evacuate the site and save the building and as much as possible of the work it contains.
"I know from speaking to Professor Tom Inns that GSA is determined that the School will recover, and rebuild and renew the Mackintosh building and what it stands for. He can count on support from friends of the GSA in Scotland and around the world, including the Scottish Government.
"We have already invested heavily in the School in recent years, contributing around £55 million to the new Reid building and to conservation of the Mackintosh building.
"We know the restoration will run into millions of pounds, and we are committed to strongly supporting the funding effort required. The Scottish Cabinet will discuss the issue at our meeting in Rutherglen on Tuesday, where we will make an announcement on the restoration plans."
Around 200 firefighters have been involved in the operation, which at its height saw 16 appliances at the scene, the Scottish Fire and Rescue Service said.
Chief officer Alasdair Hay said: "The firefighters who responded to this incident demonstrated incredible courage, skill and determination to prevent the complete destruction of this iconic building and its contents.
"Choosing to fight a fire of this scale from inside the building is a risk for firefighters and requires the highest standards of professionalism.
"Those involved in this incident were predominantly drawn from greater Glasgow and they were certainly very aware of the importance of the Mackintosh to the city. We have all been conscious of the fact this is also a building that houses the hard work of Glasgow School of Art students, especially at this time of year.
"Operating in extremely dangerous, challenging conditions our crews conducted highly aggressive firefighting operations and implemented an effective and informed salvage plan.
"By working very closely with staff from the art school, we were able to identify items and target our efforts to recover items of great importance and save everything that could possibly be saved."
He said efforts to stop the blaze engulfing the entire building were helped by early decisions and aggressive fire fighting.
A joint investigation with Police Scotland will get under way into the circumstances surrounding the fire.