Fire chiefs today made a full assessment of the damage and concluded that 90% of the building had survived along with 70% of its contents.
A statement from Muriel Gray on the Glasgow School of Art website confirmed that the iconic library had been lost however the school’s archives were safe along with some student and staff work.
The school also said that they were confident that they could recreate the Mackintosh library using similar materials.
It read: “Bad news first is that we have lost the iconic and unique Mackintosh library. This is an enormous blow and we are understandable 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 fire-fighters up the west end of the main staircase and containing the fire.
“Also after ensuring no lives were in peril they displayed an impressive understanding of the precious nature of the building, and due to their careful and meticulous handling of each developing situation the damage is considerably less than we dreaded. We have run out of words with which to thank them, but the school has most certainly gained a new gallery of heroes.
“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.”
The fire service has yet to confirm the cause of the blaze which some students have suggested started in the basement when a spark from a projector caught a piece of foam.
Students were busy putting the finishing touches to their work in preparation for the art school’s annual degree show when the fire broke out at around 12.30pm.
No one was injured in the fire but students, art lovers, architects and Glasgow officials spoke of their sorrow at seeing the “iconic” building in flames.
As well as housing one of Europe’s leading art schools, the listed Mackintosh-designed building, completed at the turn of the 20th century, is a tourist attraction in its own right.
The UK Government said it will contribute to the costs of restoring the art school.
Speaking in Glasgow today, Chief Secretary to the Treasury Danny Alexander said: “We’ve seen the appalling damage to the Glasgow School of Art.
“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.”
He added: “This is going to be a costly business but it’s a very important landmark for the whole of the UK so we stand ready to provide an appropriate share of the funds that will be necessary to bring this hugely important building back to life.”
Mr Alexander said the Government would contribute “in the millions, if necessary” to restore what he described as a “priceless gem”.