Fire fighters battle a blaze at the Mackintosh Building at the Glasgow School of Art for the second time in four years. Photo by Jeff J Mitchell/Getty Images.

Fire fighters have fought a blaze for the second time in four years at the Glasgow School of Art’s historic Mackintosh building. This time the destruction is far worse: construction experts fear that the shell of Charles Rennie Mackintosh’s landmark building will have to be torn down as much of it is in danger of collapse. To rebuild “the Mac,” as it is known, could cost at least £100 million ($132 million), the Scotsman newspaper reports, “or double that,” according to Bill Hare, a professor of construction management at Glasgow Caledonian University.

The devastating fire broke out late on Friday night at the Scottish art school. Around 120 firefighters tackled the blaze, which has left the building a smoldering ruin. The fire spread with rapid intensity, damaging the Campus nightclub next door as well as the O2 ABC music venue. There were no casualties. The First Minister of Scotland, Nicola Sturgeon, visited the site and called the fire “heartbreaking.” She is reported to have said that the Scottish Government is ready to “do anything we reasonably can to help ensure that the building has a future.”

The fire in the art school started just as a £35 million ($46 million) project to restore the Art Nouveau building was nearing completion after a fire had destroyed the school’s Mackintosh-designed library in 2014. A sprinkler system was being installed as part of the restoration work. The 2014 fire was started accidentally by an art student’s project, when gases from a foam canister were inadvertently ignited. The cause of the second fire is being investigated.

One of the oldest art schools in the UK, Glasgow’s alumni include Douglas Gordon, Simon Starling, and Jenny Saville. It has produced eight Turner prize nominees and two winners: Gordon and Starling. There has been an outpouring of empathy from the art world in response to the fire. Scottish painter and former alumni Alison Watt took to Twitter among many other notable graduates. “My heart is breaking,” she wrote. “I just can’t watch the footage of Glasgow School of Art in flames. I feel physical pain. It’s unbearable…”

In 2014, the US architect Steven Holl completed a new building for Glasgow’s celebrated art school. Known as the Reid, it is across the street from “the Mack,” and escaped damage by the weekend’s fire. A spokeswoman for the architect calls the latest fire at the art school “a double tragedy” and “beyond belief.” She says: “With his competition winning design in 1896, Mackintosh realized a deeply original creative landmark at the birth of modern architecture. Our 2009 design for the Reid building was made in the spirit of preserving his masterpiece.”