SADNESS over the fire that ravaged Glasgow School of Art’s Mackintosh building on Friday turned to anger last night, as experts warned the A-listed landmark could cost as much as £200 million to rebuild.

A clamour is now growing for answers on what sparked the blaze at the world-famous “Mack”, which was undergoing a £35m restoration following another fire that tore through the building in 2014.

But last night Kier Construction Scotland, which has day-to-day control of the site, refused to answer questions on whether sprinklers were in operation, amid reports a fire suppression system was in place but not ready for use.

Sources at the art school also said yesterday it may be up to six months before investigators can say officially what caused the disaster.

Crews were still damping down flames yesterday, with Chief Fire Officer Alasdair Hay, of the Scottish Fire and Rescue Service, describing it as one of the most significant and “heartbreaking” fires he had seen in his career.

It is understood the blaze at the Mackintosh building began in its east wing, engulfing the Charles Rennie Mackintosh masterpiece and spreading to nearby premises, including the popular music venue the O2 ABC.

By the time the first firefighters arrived on the scene only four minutes later on Friday night, it was already “well established”.

Mr Hay acknowledged the public was urgently seeking answers over the causes of the fire, but refused to speculate on its cause or rapid acceleration.

Roger Billcliffe, the leading Mackintosh expert, said answers were needed, but “don’t hold your breath, we’re still waiting for answers about the 2014 fire”.

He added: “It’s well known that buildings such as Charles Rennie Mackintosh’s art school are most at risk during building work – look at Hampton Court and Windsor Castle, both extensively damaged, rebuilt and restored. So what precautions were taken at Renfrew Street? Any? None?

“The restoration of the school seems to have been remarkably successful, but it was £35m of unneeded expenditure.

“Now it is tragically wasted. We don’t know the cause of this latest fire, but don’t be surprised if it turns out to be linked to the 2014 fire, through exposure of the building to implicitly dangerous rebuilding operations.”

The contract held by Kier Construction Scotland, which includes restoration of the Mackintosh building’s roof before restoring the west wing and upgrading the east wing interior, was scheduled to be completed by the end of this year.

Kier refused to comment yesterday on whether fire sprinklers were in operation, although reports suggested they had not yet been fully installed.

A spokeswoman said: “We are working closely with the Scottish Fire and Rescue Service in its investigation and as such it would be inappropriate to comment further while an investigation is ongoing.”

The future of the building appears to be in the balance. One expert, Billy Hare, Professor in Construction Management at Glasgow Caledonian University, has said a “consensus is beginning to grow” that demolition may be necessary.

He said the most expensive rebuild option would be a brick-by-brick deconstruction of the entire Mackintosh Building, resulting in a “replica” of the world famous structure. According to Mr Hare, this would cost at least £100m.

He added: “That is a starting point for work of this scale, it could easily rise to double that or even more. It is sadly questionable what, if anything, will be left that could be salvaged, restored or recreated after this fire.

“It remains to be seen if it will be possible to retain a facade from the current building.”

Last night Muriel Gray, the chairwoman of the board of Glasgow School of Art, said it was “an understatement to say everyone is utterly devastated but, as usual, the GSA executive team, staff and students, have been outstanding, positive and supportive”.

She added: “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.

“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.”

Scottish Secretary David Mundell and Scotland’s Culture Secretary, Fiona Hyslop, have said the fire service investigations into the cause of the blaze should be allowed to progress before any other decision is taken.

After the 2014 fire, caused by flammable gases from expanding foam being ignited by a hot projector in a degree show, an official report took six months to be issued.

Ms Hyslop said: “I can understand people want lots of their questions answered but clearly we’ve got to have the process in place first, we have to have the fire investigation first, and I think we should give people the time to carry out those very responsible duties to best effect and that will give us clarity of what is possible going forward.

“The sensible thing to do is to find out what the source of the fire was and how that spread in the initial stages. All these questions will be addressed by the fire investigation.”

At Westminster, Scottish Labour members will attempt this morning to force a UK Government minister to go to the Commons despatch box to answer questions about the art school blaze.

Questions are also emerging over insurance liability following the damage caused by the fire. One specialist, who asked not to be named, said firms involved would be asking serious questions as they try to gauge who should pay out and how much.

He said: “There will be questions about that – whose liability, which insurer, and is there enough to cover what will be in the hundreds of millions?”

Chief Fire Officer Hay said the fire service had done all it could to protect the integrity of the building.

He said: “Our fire fighters have been heroic, and done everything they can, to protect and save this building and we are working very hard with colleagues to make sure we do save the structural integrity of the building."