CALLS for a public inquiry into the fire that gutted Glasgow's world-famous School of Art have been rejected as premature by senior politicians as experts estimated rebuilding costs could top £100 million.

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

Around 50 firefighters are still at the scene of the blaze, which broke out on Friday night, engulfing the Charles Rennie Mackintosh masterpiece and spreading to nearby buildings including the popular music venue the O2 ABC.

A few pockets of fire remain at the site with crews using thermal imaging cameras to identify any remaining hot spots.

The blaze is the second in four years to hit the Mackintosh Building, which was undergoing a multimillion-pound restoration project to return it to its former glory.

Ms Hyslop told the BBC's Sunday Politics Scotland programme that no one had yet been able to enter the building.

She explained once it had been declared safe, building control and Historic Environment Scotland [HES]officials would assess the situation and the exterior of the art school.

On calls for a public inquiry, the Scottish Culture Secretary 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 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. We need them to do their job initially and that is very, very important," stressed Ms Hyslop.

She confirmed HES had taken a digital record of the building and its contents after the previous 2014 fire but noted: "The severity of this is very severe so I'm not giving any commitments at this stage."

Speaking on the same programme, Mr Mundell said: "I don't at this stage think there's a case for a public inquiry unless someone can bring forward some exceptional reason.

“The initial inquiries should take place as would normally follow a fire into what was the cause and what were the related circumstances," he added.

Earlier, Scottish Fire and Rescue Service group manager Martin Hill said: "This has clearly been a protracted incident and today we are still very much in a firefighting phase.

"Our firefighters have been working effectively throughout the night and we are continuing to dampen down any remaining pockets of fire.

"We are also using thermal imaging cameras to identify any hidden hotspots and will continue, working alongside partners, to assess our priorities and our tactical firefighting operation over the course of the day.”

He said the fire service would remain at the scene for as long as it took, stressing how it was absolutely committed to preventing any further damage to surrounding properties and ensuring the area was made safe.

"I would like to express a sincere thank-you to our crews on the ground and our firefighters in operations control for continuing to effectively co-ordinate our resources as well as our partners along with the wider community."

The fire service made clear it was still too early to determine the cause of the fire.

The UK and Scottish Governments have said they stand ready to provide support, including financially, to the art school as it assesses what the future may hold.

But experts have estimated the cost of rebuilding the gutted Mackintosh Building would be at least £100m, if anything can be salvaged at all.

Fire risk and construction management academics at Glasgow Caledonian University have put forward their views on the extent of the damage and how big a repair bill would be.

Professor Billy Hare said: "The damage to the School of Art appeared to be overwhelming, much worse than the last fire from which recovered materials were painstakingly analysed and used in the refurbishment of the building.

"It is sadly questionable what, if anything, will be left that could be salvaged, restored or recreated after this fire.”

He said it remained to be seen if it would be possible to retain a facade from the current building. If not, Prof Hare explained how damaged buildings had been taken down almost stone by stone in the past and rebuilt with a new, internal frame.

"This sort of project will cost a great deal more than the estimated £35m after the last fire in May 2014".

A conservative estimated cost for full rebuilding of the damaged building would be at least £100m, he added.

The academics believe it is likely the fire started in the upper levels of the property, due to the roof appearing well alight in the early stages.