News: the international architecture community is in mourning for Mackintosh's masterpiece as tributes pour in for "immeasurably" influential building. 

Steven Holl and Chris McVoy, who together designed the GSA's new Reid Building across the road from Mackintosh's original art school, said that the fire was "unbelievably tragic for architecture and the history of architecture".

"This is an unimaginably sad and deeply spiritual loss," they said. "We are so sorry especially for all the community of the School. We are thankful that the students are safe. The loss to their future education is devastating."

Fire fighters are still on the scene of the fire in Glasgow, which is thought to have started in the basement of the building before spreading up the west side and across the roof. Read our previous story for more information.

Update: firefighters say they have saved 90 per cent of the structure of the building.

Architect Mark Kilkenny, who has been participating in a feasibility study for the adjacent Mackintosh School of Architecture (Bourdon Building), was working on the project when news of the fire broke.

"I was working on proposals for how the architecture building might have a more positive dialogue with its masterful neighbour," said Kilkenny.

"I’m a relative newcomer to and part time member of the GSA family and feel heartbroken. I can only begin to imagine the devastation for the staff and students for whom that building is a gentle but fun Grandpa."

In a statement issued this afternoon, Ian Connely, the president of Royal Incorporation of Architects in Scotland, said that the value of the building "goes well beyond Glasgow or even Scotland".

"It is a work of architectural heritage of world renown and its influence on 20^th century architecture is immeasurable," said Connelly.

"Scotland has seen the loss of an international treasure which reflects the genius of one of our greatest ever architects and the whole of the architectural profession in Scotland will, I am sure, join with me in sending out a message to the students and staff of the School and all those who have been associated with this building over the decades, a message of sorrow and commiseration at this terrible, terrible news."

Royal Institute of British Architects president Stephen Hodder said: "The most important work by Charles Rennie Mackintosh, an architect of international significance, Glasgow School of Art is held in the highest regard by architects and the public alike."

"Damage to a building of such immense significance and uniqueness is an international tragedy. It is irreplaceable."

Top image by Jean-Pierre Dalbera.