The future of Glasgow School of Art’s historic Mackintosh Building has been plunged into uncertainty after it was gutted by a large fire on Friday night.

Fire crews said the blaze broke out just before 11.20pm and that several engines with specialist equipment had been sent to the scene.

Stunned onlookers said a large section of Sauchiehall Street was blocked off while efforts continued to bring the fire under control.

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They also said it looked as if the building was sustaining heavy damage, with flames and smoke billowing from the windows.

It is not currently known if there were casualties.

The Mackintosh building - considered one of designer Charles Rennie Mackintosh’s masterpieces - was badly damaged by a large fire in May 2014 which broke out in its basement and quickly spread upwards.

A spokeswoman for the Scottish Fire and Rescue Service said last night: "We are currently in attendance in the Mackintosh Building in the Glasgow School of Art.

"Operations Control mobilised a number of fire engines to the scene after the call came in at 11.19pm and we are currently still tackling the fire."

Staff at GSA have confirmed that the blaze broke out in the school's Mackintosh Building.

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In a tweet, they said: "There is a fire at the Mackintosh Building.

"The fire brigade are currently on scene.

"We will report back with news updates as soon as possible."

David Pratt, The Herald’s foreign editor, who studied and lectured at Glasgow School of Art, was watching crews battle the blaze from Garnethill.

He said: “I saw the fire in 2014 and this is way worse than what I saw last time. 

“They are having huge problems controlling it.

“It’s a horrendous thing to watch the building being ravaged all over again.

“I think the Mackintosh building is finished. It’s absolutely finished.” 

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Expressing her concern, First Minister Nicola Sturgeon tweeted: "Thoughts with you @GSofA - I know @scotfire_glasgo will be doing everything they can."

Onlookers posted pictures and videos on social media.

Rocco Giudice said: "Glasgow Art School on fire again. Gutting!"

Arun Day tweeted: “Everyone stay clear of Glasgow Art School and the surrounding areas. I was playing in Campus and everyone got evacuated.

"Massive fire at the Art School. Hope everyone in and around the school is safe!

"All of Sauchiehall street is blocked off. Police and Fire services everywhere."