Restoring Glasgow School of Art’s fire-ravaged Mackintosh building to its previous architectural glories could cost hundreds of millions of pounds and take years of painstaking work, according to a leading construction expert.

As fire investigators begin looking for the cause of the fire and building control officials determine what can safely be saved, a leading construction expert has outlined three possibilities.

Professor Billy Hare, lecturer in construction management Glasgow Caledonian University, has said that a brick-by-brick restoration of the severely damaged building is one of three options currently open to the Art School.

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Speaking after visiting the building’s remains on Sunday, the researcher said there was a “growing consensus that it will probably be declared structurally unsound”.

He added: “From the intensity of the fire there appears to be multiple structural problems on the outside of the building.

“Based on what I have seen the site bears similarities to the fire which started at Victoria’s nightclub in March in terms of intensity and scale.

“Given that what we are seeing is a demolition of these buildings, the logical conclusion is that the damage could be just as widespread.

Read more: Glasgow Art School fire: Sprinklers ‘were NOT fully fitted’

He outlined three options for the future of the Mackintosh Building.

A conventional demolition, and new rebuild which could cost around £50m would be the cheapest option, according to the professor.

A second option of facade retention, would result in a new structure being raised on the site of the Mackintosh, retaining many of the well-known architectural works previously on both the exterior and interior of the building.

This could cost total up to anything between £75million and £100m.

The most expensive option would be a brick-by-brick reconstruction of the entire Mackintosh Building, resulting in a “replica” of the world famous structure.

Read more: Glasgow Art School fire: Sprinklers ‘were NOT fully fitted’

This is possible because the site was digitally recorded after the fire in 2014.

According to Professor Hare, this could appear as a replica of the previous building, but would cost at least £100m.

“That is a starting point for work of this scale, it could easily rise to double that or even more.

Government ministers said they were ready to offer help.

First Minister, Nicola Sturgeon said “I’ve spoken to the principal of the art school already and the Scottish Government stands ready to do anything we reasonably can to help ensure that the building has a future.

“It’s too early to say what that might entail or what that might look like.”

David Mundell, Scottish Secretary said: “I am devastated to hear of fire at Glasgow School of Art. It is only a fortnight since I was there to see the progress on the restoration, and my heart goes out to all those who had worked so hard.

"The UK Government stands ready to help, financially or otherwise.”

Art School bosses said at this stage they were hopeful of saving the famous building Muriel Gray, chair of the Board of Governors, said: “We now have a difficult waiting game until Scottish Fire and Rescue Service, Glasgow City Council and associated agencies have completed their investigations into the condition of the building.

Read more: Glasgow Art School fire: Sprinklers ‘were NOT fully fitted’

"We remain hopeful of as positive an outcome as possible because it is clear that the love for the Mackintosh and recognition of its importance to Glasgow and the wider world is shared by absolutely everyone”.

Tom Inns, director of GSoA said the immediate priority was continuing operations for staff and students.

