The investigation into what caused the blaze at the Glasgow School of Art’s Mackintosh building will be "complex and thorough", according to Scottish Fire and Rescue Service chief.
Assistant chief officer David McGown said it would take some time to establish the full facts and circumstances regarding what happened at the building where Kier was undertaking a £35m restoration project following an earlier fire in 2014.
The fire, which broke out on Friday 15 June has now largely been extinguished, although three fire engines and a high-reach appliance were still at the scene yesterday.
At its height, more than 120 firefighters attended the incident.
McGown, who is the Scottish Fire and Rescue Service director of prevention and protection, 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.
"It is of vital importance that we ensure the full facts and circumstances of this incident are clearly established."
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."