Fire chiefs are confident they will discover how the blaze which engulfed the Glasgow School of Art (GSA) started – but stressed the “very complex” investigation will take time.

Four appliances remained at the scene at midday on Monday following the fire, which broke out in the historic Mackintosh Building at 11.19pm on Friday and spread to nearby buildings including the O2 ABC.

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

The Scottish Fire and Rescue Service (SFRS) said the investigation into the cause of the blaze has already started and they believe they will be able to pinpoint how it started.

The Mackintosh building was engulfed in flames on Friday night (Douglas Barrie/PA)
The Mackintosh building was engulfed in flames on Friday night (Douglas Barrie/PA)

Assistant Chief Officer David McGown of the SFRS said: “The investigation into this devastating incident has already commenced.

“Our fire investigation team has started gathering information and, working alongside our police partners, will look at various sources of information to establish exactly what has happened here.

“However, I would like to stress that this is a very complex process and will take time.”

He added: “Our Fire Investigations team are specialists in their own field.

“They will look at every aspect of this incident – including the cause of the fire, how it spread and what safety measures were in place.

“We understand the need for clarity here and why so many want to know how this happened, but I would again like to reiterate that we need to establish the full facts and circumstances of this incident – and this will take time.”

Earlier Mr McGown told BBC Good Morning Scotland “I can give this guarantee that we will find out what happened in this fire, what the cause was and what the cause of spread was.”

The fire at Glasgow School of Art could be seen from across the city (Peter Swanton/PA)
The fire at Glasgow School of Art could be seen from across the city (Peter Swanton/PA)

At the height of the incident more than 120 firefighters were involved in fighting the blaze. There have been no reports of any casualties.

A few pockets of fire remain which crews were still working to extinguish on Monday.

The blaze has shocked and saddened people in Glasgow and beyond including leading figures in the worlds of art and music.

Singer Annie Lennox tweeted: “So sad and disappointed for everyone affected by this 2nd devastating fire… (who would believe??!!) at Glasgow’s historic and renowned Charles Rennie Mackintosh art school. .. the renovators, students, staff, alumni, noble fire fighters and everyone in Glasgow.”

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

However GSA bosses said they remain hopeful of a positive outcome for the Mackintosh Building,

Meanwhile, Labour MP for Glasgow North East Paul Sweeney, who is director of the Glasgow Building Preservation Trust, said that having been escorted round the building by SFRS, it is clear the interior is almost entirely lost – but the main structural beams appear to still be largely intact, giving hope some of it can be saved.

Tweeting about his visit he wrote: “The Mack will endure.”

He told the BBC: “Whatever needs to happen to make this building realised again as Mackintosh’s vision has to happen.”