Firefighters are continuing to fight a major blaze at the A-listed Glasgow School of Art - one of Scotland's most iconic buildings.
Eyewitnesses said the fire appeared to have started when a projector exploded in the basement of the Charles Rennie Mackintosh building just before 12:30.
Fire Officer Alasdair Hay said the main blaze was out but there were still pockets of fire within the building.
Everyone in the building was said to have escaped safely.
The Mackintosh building, completed in 1909, is "unique" in that it is a working art school as well as a work of art.
From the facade to the fixtures and fittings every detail shows the craft of Charles Rennie Mackintosh, Scotland's most-lauded designer.
The Scottish Fire and Rescue Service (SFRS) said fire crews had managed to salvage some of the objects contained in the building and structural engineers were assessing the safety and stability of the building.
Fire crews were on the scene within four minutes of the alarm being raised.
Search and rescue teams entered the building wearing breathing apparatus and led a number of people to safety. There were no reports of any casualties.
Final year students were said to have been preparing for their end-of-year degree show in the building when the blaze broke out. The deadline for submissions to the degree was 17:00.
SFRS Chief Officer Alasdair Hay said there had been "significant spread" of flames within the building but would not comment on speculation it did not have a sprinkler system installed.
He added that it was still too early to say how extensively the art school had been damaged, or what the cause of the blaze had been.
But he said officers were "well aware of the iconic status of the building".
Police have cordoned off Renfrew Street, and smoke was also drifting across the M8. Large crowds of students and onlookers gathered near the scene, with several people in tears as they watched the events unfold.
Fire appliances from across Glasgow were joined by specialist crews from other areas of Scotland, with firefighters seen pouring water on the building from a high ladder as flames blew windows out.
The crews are expected to be on site until well into the night as efforts to put out the last of the flames continued.
Hugh Thornhill, a second year student, said: "I was helping one of the fourth years set up their exhibit and suddenly the alarm went off.
"We didn't think it was anything but we had to go out and then we saw smoke coming out and realised that it was really bad. It got to the point where flames were coming out of the top floor.
"All that effort is gone, everyone's work on that side of the building is ruined. Even if it didn't catch fire it will be damaged extensively.
"The degree show next month is pretty much a bust now, it's sad."
Broadcaster Muriel Gray, a former student and current chairwoman of the school, arrived and burst into tears when she saw the building in flames.
Ms Gray told BBC Scotland she was "heartbroken" to see the "most amazing building in Glasgow" go up in flames.
Speaking later, she added: "It has been a devastating day for everybody involved in Glasgow School of Art. We want to make it clear we are so grateful to the fire service. It's a very black day."
Asked how the building could be restored, Ms Gray said: "We don't know what's been destroyed. It's a waiting game."
Scotland's First Minister Alex Salmond said on Twitter: "Thoughts with staff & students at @GSofA - awful to see destruction of this iconic building and students work."
Austin Yuill, who works as a chef at the art school, told the BBC: "I've been moved two streets away from the Mackintosh building but before we left the place was completely ablaze all down the west side of the building.
"I'm told it started in the basement and it's worked its way all the way up through the five floors.
"As far as I know it started from a spark which has gone on to foam, expanding foam."
Asked how busy the art school was, he said: "It would be very busy because we're working up to the end-of-year assessments, so all the students were installing their work today all over the Mackintosh building. There are a lot of very upset students here."
He added: "Quite apart from it being voted the best building of the last 175 years, it is a major tourist draw and has an incredible reputation as an art school. This is really terrible."
Charles Rennie Mackintosh is lauded as Scotland's most influential architect and designer, with the art school building which bears his name considered by many to be his greatest masterpiece.
Mackintosh was a 28-year-old junior draughtsman at a Glasgow architecture firm when he drew up the designs for the building, which features distinctive heavy sandstone walls and large windows.
The dramatic art nouveau design took about 12 years to be completed, opening in 1909, but it signalled the birth of a new style in 20th Century European architecture.
The president of the Royal Incorporation of Architects in Scotland, Iain Connelly, said the value of the building "goes well beyond Glasgow or even Scotland".
He added: "It is a work of architectural heritage of world renown and its influence on 20th century architecture is immeasurable. Scotland has seen the loss of an international treasure which reflects the genius of one of our greatest ever architects."
In recent years, Glasgow School of Art has produced many of the UK's leading contemporary artists such as Douglas Gordon and David Shrigley and three recent Turner Prize winners: Simon Starling in 2005, Richard Wright in 2009 and Martin Boyce in 2011.
Other former students include actors Robbie Coltrane and Peter Capaldi and artist Peter Howson.