Firefighters finally declared the site safe enough to hand control back to the Glasgow School of Art (GSA) after a week of rescue work to try and save the majority of the original school building, following a fire that destroyed significant areas of its west wing last Friday, including the library and a studio above it.
The last members of the Scottish Fire and Rescue Service were seen off by an honour guard of students and staff as well as a Scottish piper.
"We did not want to miss this opportunity to once again register our deep and heart felt thanks to the Scottish Fire and Rescue Service who over the last week have been quite simply amazing," said Glasgow School of Art director Tom Inns.
Mackintosh's building primarily housed the school's Fine Art department, as well as a gallery that hosts exhibitions and the students' annual degree show. Earlier this week Dezeen reported that up to 90% of the building and 70% of its contents were thought to have been saved by the actions of the fire service.
Staff from heritage body Historic Scotland are now working with the GSA to begin the first phase of reconstruction work.
A team from the GSA's Digital Design Studio has laser scanned the Western Gable of the building to create a 3D plan of what survived the fire and today specialist stonemasons began "deconstructing and laying aside a small section of the uppermost part of the Western Gable for conservation" said the school.
Stonework that has to be removed will be taken to Historic Scotland's Glasgow Cathedral depot for conservation and stored until they can be reinstated into the fabric of the building.
Further work will take place after the building's condition has been fully assessed, and the school is currently investigating insurance issues and finding the "appropriate people" to work on the project.
Students have been allowed back in to the design and architecture buildings to continue work on their end-of-year shows and projects. Fine art students were able to meet with their tutors and have been told that their assessments and graduations will go ahead as originally planned, despite work being lost in the fire. A number of students will also receive "phoenix" bursaries, as reported by Dezeen earlier this week.
Meanwhile, members of the public have already donated over £70,000 towards the rebuilding efforts, partially via the school's online funding raising page on The Big Give.
Offers of practical help have come from a variety of professionals, including curators, conservationists and counsellors.
A spokesperson for the school said they had been "overwhelmed with the level of genorosity".
The fire, which is thought to have started in the basement and spread up through the west wing of the building before reaching across the roof, triggered an outpouring of dismay from the architecture and design communities last week.
"It is internationally famous – architects around the world pay homage to it," Sunday Times critic Hugh Pearman told Dezeen. "It is such a significant national monument that money will be found to restore it but it will never be same."
"I remember going through the studios when I went up there this year, and seeing original Mackintosh doors spattered with decades of paint from students, door handles worn by students. It's those marks of time which added to it and made it somehow even better than it would have been when it was brand new."
Steven Holl and Chris McVoy, who together designed the GSA's new Reid Building across the road from Mackintosh's original art school, said that the fire was "unbelievably tragic for architecture and the history of architecture".
Top image by Jean-Pierre Dalbera.