The discovery of asbestos within the Mackintosh Building of the Glasgow School of Art led to a delay in installing a fire suppression system, which was not in operation at the time of the disastrous fire in May.

Professor Tom Inns, director of the school (GSA), said the discovery of the dangerous substance and delay in installing the equipment formed part of a series of events that led to the blaze which destroyed the Mackintosh Library and much of the west end of the historic building.

The detail emerged yesterday as the official Scottish Fire and Rescue Service (SFRS) investigation Report into the blaze was released by the GSA.

One person was assembling work made from foam panels, fastened to three walls of a space made from chipboard and wooden studs, with one wall left blank to receive projected images from the projector mounted on the opposite wall.

The person, not named as a student or staff, was filling in gaps between the panels by applying foam directly from a canister when the flammable gases in the tin - isobutane, propane and dimethyl ether - were sprayed close to the projector and drawn into its cooling fan.

The projector, purchased in 2008 by the GSD and not defective according to the report, ignited the gases with its electrical components, burning through the plastic of the projector and then igniting the foam walls placed directly behind it.

Speaking to The Herald, Professor Inns revealed that students had been told not to use expanding foam dispensed from canisters.

Professor Inns, who said no one was being disciplined for the incident, said: "That is not something that should happen. It was an accident and an error of judgement."

The report found that the fire's rapid progress through the Charles Rennie Mackintosh designed-building was aided by timber-lined walls and voids, and ventilation ducts running both vertically and horizontally throughout the building.

It says "a fire suppression system, designed to enhance existing fire protection measures, was being installed and was in the latter stages of completion; at the time of the fire the system it was not fully commissioned and was not operational."

The suppression system, which dispenses a fine mist of water on fires, had been delayed because contractors found asbestos in the foyer area of the building, which delayed completion by two weeks - meaning that it was not working when students were installing their works for degree shows.

Professor Inns, maintained that the fire was an accident and no one is being held to blame.

Police categorised the fire as an accident within days.

Professor Inns said he is sure exhibitions will be held in the Mackintosh Building again, but would not commit fully to holding the full Fine Art Degree Show in the building again.

The fire started in Studio 19, in the north basement of the west wing of the building as students were assembling their degree shows.

The flames spread through Studio 19, igniting timber panelling, and travelling through voids in the walls into Studio 31 on the ground floor, directly above.

The fire, aided by voids in the walls, spreading unchecked to Studio 32 and through voids to the Mackintosh Library above. The report says: "The construction, layout, and high fire loading (timber furniture, panelling and books) meant that the room and its contents became totally involved in the fire."

In addition to ventilation ducts, a vertical service void ran "the entire height of the building to roof level and acted like a chimney. It allowed flames, hot gases and smoke to travel vertically."

The School of Art has commissioned an external review of its management of the incident.